August 12, 2020


The substrate you stick with? The idea of Cation Exchange Capacity...

The botanical-style aquarium "movement" has begun to really evolve. It's been interesting to see the fine work of so many hobbyists really push the envelope out a bit.

One of the things you might have noticed lately is that we're looking at more and more ways to create realistic, functional, and aesthetically unique aquariums. It's not just about having a large selection of botanical's about experimenting with them and other tangential natural materials to help recreate some of the aspects of the natural habitats which we admire so much.

Like, substrates, for example.

As you know by now, we've been developing (seems like forever) a line of substrates, designed to help you experiment at recreating various types of aquatic habitats, such as the igapo and varzea of South America, among others. And when you develop new products like substrates, you have to consider how the end users will embrace them (or, IF they will embrace them!), and how they will apply them to their work.

Inevitably, there are questions.

The genesis for today's piece was a message that we received from a member of our community, who was curious about some interesting aspects of botanicals and of our substrates- specifically about their "CEC" factor- something which aquatic plant fans consider when evaluating substrates for growing their plants.

What is "CEC?"

Cation Exchange Capacity (CEC) is the ability of a material to absorb positively-charged nutrient ions. This means the substrate will hold nutrients and make them available for the plant roots, and therefore, plant growth. CEC measures the amount of nutrients, more specifically, positivity changed ions, which a substrate can hold onto/store for future use by aquatic plants.

Thus, a "high CEC" is important to many aquatic plant enthusiasts in their work.  While it means that the substrate will hold nutrients and make them available for the plant roots. However, it doesn't indicate the amount of nutrients the substrate contains. 

For reference, scientists measure cation exchange capacity (CEC) in milliequivalents per 100 grams ( meq/100g).

To really get "down and dirty" to analyze substrates scientifically, CEC determinations are often done by a process called "Method 9081A" of EPA SW- 846. CEC extractions are often also analyzed on ICP-OES systems. A rather difficult and expensive process, with equipment and methods that are not something hobbyists can easily replicate!

As you might suspect, CEC varies widely among different materials. Sand, for instance, has a CEC less than 1 meq/100 g. Clays tend to be over 30 meq/100 g. Stuff like natural zeolites are around 100 meq/100g! Soils and humus may have CEC up to 250 meq/100g- that's pretty serious!

What nutrients are we talking about here? The most common elements which come into play in the context of CEC are iron, potassium, calcium and magnesium. So, if you're into aquatic plants, high CEC is a good thing!

Of course, this is where the questions arise around the substrates we play with.

It makes sense, right?

Our "Nature Base" substrates that we are going to release soon do contain materials such as clays and silts, which could arguably be considered "higher CEC" materials, because they're really fine- and because higher surface area generally results in a higher CEC. The more surface area there is, the more potential bonding sites there are for the exchange to take place. Alas, nothing is ever exactly what we hope it should be in this hobby, and clays are often not all that high in their CEC "ratings."

Now, the "Nature Base" substrates are what we like to call “sedimented substrates”, because they are not just sand, or pellets of fired clays, etc. They are a mix of materials, and DO also have some soils in the mix, too, which are also likely higher in CEC. 

Promising, from a CEC standpoint, I suppose!

However, they were really created to replicate the substrate materials found in the igapo and varzea habitats of South America, and the overall habitat- more "holistically conceived"-not specifically for plant growth. And, in terrestrial environments like the seasonally-inundated igapo and varzea, nutrients are often lost to volatilization, leaching, erosion, and runoff..

So, it's important for me to make it clear again that these substrates are more representative of a terrestrial soil, and are not specifically formulated to grow aquatic plants luxuriously. The decomposition of detritus and leaves and such in our botanical-style aquariums and "Urban Igapo" displays is likely an even larger source of “stored” nutrients than the CEC of the substrate itself, IMHO. 

An added benefit of these types of substrates is that they will provide a home for beneficial bacteria- breaking down organics and helping to make them more available for plant growth. 

That being said, the stuff DOES grow aquatic and riparian plants and grasses quite well, in our experience! Yet, I would not refer to them specifically as "aquatic plant substrates." They're not being released to challenge or replace the well-established aquatic plant soils out there. They're not even intended to be compared to them!

Remember, our substrates are intended to start out life as "terrestrial" materials, gradually being inundated as we bring on the "wet season." And because of the clay and sediment content of these substrates, you'll see some turbidity or cloudiness in the water. It won't immediately be crystal-clear- just like in Nature. And no, we haven't done CEC testing with our substrates...It's likely that in some future, some enthusiastic and curious scientist/hobbyist might just do that, of course!

I can't stress it enough: With our emphasis on the "wholistic" application of our substrate, our focus is on the "big picture"- not specifically aquatic plant growth. Yet, hobbyists being hobbyists, I'm sure that they will evaluate them based upon this ability, so I felt that I should at least address this topic at this juncture.

High CEC certainly can help grow aquatic plants in these or other substrates; however, it's important to note that it's only a small component of of nutrient availability for the plants. 

And of course, if we go back to the idea of CEC being a "measure" of a material to absorb positively charged nutrient ions, the question comes full circle to, "Do botanicals themselves have "CEC" capabilities?"

The answer is, I'm not really sure!

Yet, the postulating non-scientist in me can't help but wonder if, much like loam or humus, these plant-derived materials have this unique ability. I mean, we talk about botanicals and leaf-litter beds as attachment points for biofilms, fungal growth, and other organisms, so it makes sense to at least postulate that they have the capacity to sequester some nutrients as they break down, right?

I think that it does. I mean, at the very least, we've played around with the idea that decomposing leaves and such comprise a sort of aquatic "mulch" for plant growth. Mulch, by definition is: "Material (such as decaying leaves, bark, or compost) spread around or over a plant to enrich or insulate the soil." What works in the garden likely works in the aquarium, in the context of "substrate enrichment", right?

I think that the possibility of utilizing botanicals along with specialized substrates as a means to grow plants and enrich the overall aquarium ecosystem on many levels is simply too irresistible to overlook. Indeed, botanicals are a sort of "substrate" in and of themselves- and that is something that's quite interesting! 

The body of experience that we as hobbyists are accumulating with botanical-style aquariums is not only resulting in greater understanding and refinement of techniques in our sector- it's "trickling back" to other sectors of the hobby, such as aquatic plants, etc.

And of course, for facilitating and elevating the idea of the "Urban Igapo"- a "transitional" aquatic/terrestrial habitat replication...something that's seldom been done before in the hobby!

And we couldn't be more excited to see that! Remember, the "substrate" that you stick with in your aquatic display can have a profound and important impact on the diversity, health, and stability for many years to come!

Here's to some exciting new experiments!

Stay excited. Stay curious. Stay observant. Stay diligent...

And Stay Wet.


Scott Fellman

Tannin Aquatics 







August 10, 2020


There's beauty in the details...

Do you need to use a filter in your aquairums?

Seriously? I mean, do you need to filter the water to crystal clarity each and every time you set up a tank? Or. do you trust your skills as a hobbyist? Can you trust that Nature will seek a balance of nutrient import and export if you stock and feed your tank correctly? 

The answers always lie in the details, huh?

I was chatting with a good fishy friend last weekend, and we were talking about our current tanks, our ideas, and our aspirations for new projects...the usual stuff you expect when fish geeks share a meeting of the minds

My friend brought up the subject of how we simply obsess over our aquariums...well, deeper than that, really. He pondered about how, as serious aquarists, we approach our aquariums by considering every little detail. Not necessarily obsessing to the point of self-limiting, mind you. Rather, just thinking through how everything that we do has a lot of potential benefits.

For example, when the subject of lighting came up, my friend, one of the best reef hobbyists I know, in addition to being an all-around "waterman" (a reefer/FW/brackish guy), pointed out that my LED lighting in my tank was set towards a far greater blue-white spectrum than made sense for a system intended to resemble a South American stream, and that the predominant colors of my fishes were reds and browns, which are accented far more by reds and greens in the lighting program.


Plus, he correctly pointed out that the blue tended to cancel out some of the vibrancy of tint in the water, much to my chagrin. So, with a few simple tweaks to the light program, we have a far more superb rendition of color than ever before. 


When you feed your fishes, you may love the convenience of frozen brine shrimp, blood worms, pellets, whatever, and tend to use that as your "exclusive" or primary food by a significant margin over other foods. I get that. Yet, it's not always the best idea if you're feeding foods that are richer, fattier, and more difficult for fishes to digest.

The idea of a well-rounded diet is really important, as fishes need a higher nutritional profile than we give them credit for to stay in top shape. And of course, different foods are better suited for different situations, such as when you're conditioning fishes for breeding, forcing growth, or helping your females recover after spawning. Each situation requires a different approach to feeding.

And more important in our context- we as botanical-style aquarium lovers need to get our heads around the fact that our systems can generate a significant amount of supplemental food.


Thinking about stocking your aquarium has never been one of those "Oh, I'll get to it later" sort of things for most serious hobbyists. Stocking is viewed as a make-or-break part of aquarium design and is rarely approached in a nonchalant manner. Nor should it be.

Taking into account the type of system you're trying to create, and the various strata and microhabitats that your target fishes inhabit within the system is vital to creating a successful, healthy, interesting system in the long term. A lot of "old timers" in the hobby will tell you that many great aquariums are indeed great because they take into account the environment within the aquarium for stocking, "optimizing", if you will, available niches within the system by selecting appropriate animals.


I mean, there are so damn many things in the hobby that you can approach in this manner...and really, this level of attention is not tedious, obligatory, or even remotely stressful. It's simply the way to create maximum enjoyment from your hobby.

I can't tell you how much I've learned about seemingly obscure and unimportant aspects of the hobby by just delving into greater detail when setting up my systems, or looking at things from a different perspective-only to realize that the benefits I've reaped from this process are far, far greater than I could have imagined.

This kind of thoughtfulness can pervade every aspect of our hobby.

So the next time you're looking at something seemingly as "pedestrian" as two or three different filter media, for example, take a moment to consider and reflect upon what each can bring to the table for your specific needs. Think beyond the marketing hyperbole; the hobby "hype", and consider how this stuff will work with   YOUR system.

You might just find yourself making some seemingly surprising decisions when you approach these types of things from the standpoint of "Why should I go with THIS particular one" as opposed to, "I need some carbon"- or whatever.

Details. Again.

They're not just mundane. They're not for getting "lost" in.

Rather, details can help you create something truly special, and can make the difference between a good aquarium and a really phenomenal one.

There's beauty in the details...

So, roll up those sleeves, pull up a chair, and ponder a bit. You might just stumble on something that changes your perspective.

Stay engaged in the process, engrossed in the fun, and attentive to the details.

Stay curious. Stay excited. Stay observant. Stay creative. Stay diligent...

And Stay Wet.



August 09, 2020


A combination of elements...

We speak very often about the flooded forests of South America and elsewhere when discussing unique ecological niches in which terrestrial materials, such as botanicals, roots, branches, leaves, and soil play a role in shaping the aquatic ecosystem which arises following the inundation.

There is something so compelling about this particular combination of materials- it's the essence of what our mission here at Tannin Aquatics is all about...The combining of terrestrial and aquatic elements, and the influence which they have on the overall ecosystem. There is so much we can learn from studying these systems that we can apply in our hobby work. 

To show you just how geeked-out I am about this stuff, I have literally spent hours pouring over pics and video screen shots of some of these igapo habitats over the years, and literally counted the number of leaves versus other botanical items in the shots, to get a sort of  leaf to botanical "ratio" that is common in these systems.

Although different areas would obviously vary, based on the pics I've "analyzed" visually, it works out to about 70% leaves to 30% "other botanical items." 

The trees-or more specifically, their parts- literally bring new life to the waters. Some are present when the waters begin rising. Others continue to arrive after the area is flooded, falling off of forests trees or tumbling down from the "banks" of the stream by wind or rain.

Terrestrial trees also play a role in removing, utilizing, and returning nutrients to the aquatic habitat. They remove some nutrient from the submerged soils, and return some in the form of leaf drop. 

Interestingly, studies show that about 70% of the leaf drop from the surrounding trees in the igapo habitats occurs when the area is submerged, but the bulk of that is shedded at the end of the inundation period. The falling leaves gradually decompose and become part of the detritus in the food web, which is essential for many species of fishes. This "late-inundation leaf drop" also sets things up for the "next round" - providing a "starter" set of nutrients, doesn't it?

The materials that comprise the tree are known in ecology as "allochthonous material"-  something imported into an ecosystem from outside of it.  (extra points if you can pronounce the word on the first try...) And of course, in the case of trees, this also includes includes leaves, fruits and seed pods that fall or are washed into the water along with the branches and trunks that topple into the stream.  

You know, the stuff we obsess over around here!

Many of these materials begin to break down during the time they are submerged, and are known  generically to ecologists as “coarse particulate organic matter.” In the waters of these inundated forest floors, there is a lot of CPOM, and the community of aquatic organisms (typically the aforementioned aquatic insects and crustaceans) has a high proportion of “shredders”, which feed on the CPOM and break it up into tinier bits called (wait for it...) "fine particulate organic matter."

Some of these "shredders" and their larvae are a direct source of food for fishes, providing a nutritious food source for growing populations in these waters. Another reason why these habitats are so abundant in fish species!

And of course, some fishes directly consume fallen fruits and seeds themselves as part of their diet as well, aiding in the "refinement" of the CPOM.  Think about the big, ugly Pacu, for example, which has specialized mouthparts suited to crushing hard-shelled fruits and seeds. This fish consumes the fruits and literally shits out seeds, helping distribute them throughout the forest! Thus, a fish helps perpetuate a tree. ("Feed a Pacu, plant a forest?" Okay., whatever.)

(Image by Wisky- used under CC BT-SA 3.0)

Other organisms make use of the fine particulate matter by filtering it from the water or accessing it in the sediments that result. These allochthonous materials support a diverse food chain that's almost entirely based on our old friend, detritus!

Yes, detritus. Sworn enemy of the traditional aquarium hobby...misunderstood bearer of life to the aquatic habitat.

Yeah, the detritus forms not only a part of the food chain in these systems- a very important part in the diet of many of our beloved's a literal physical structure that provides an area for fishes to forage, hide, and in some instances, spawn among.

A combination of elements- terrestrial and aquatic. All working together. 

Many other fishes which reside in these flooded forest areas feed mainly on insects; specifically, small ones, such as beetles, spiders, and ants from the forest canopy. These insects are likely dislodged from the overhanging trees by wind and rain, and the opportunistic fishes are always ready for a quick meal!


Interestingly, it's been postulated that the reason the Amazon has so many small fishes is that they evolved as a response to the opportunities to feed on insects served up by the flooded forests in which they reside! The little guys do a better job at eating small insects which fall into the water than the larger, clumsier guys who are more adapted to snapping up nuts and fruits with their big, gnarly mouths! 

And yes, some species of fishes specialize in detritus.

As we have discussed more times than you likely care to remember, decomposing leaves are the basis of the food chain, and the they produce forms an extremely important part of the food chain for many, many species of fishes. Some have even adapted morphologically to feed on detritus produced in these habitats, by developing bristle-like teeth to remove it from branches,tree trunks, plant stems, and leaf litter beds. 

Of course, it's not just the fishes which derive benefits from the terrestrial materials which find their way into the water. Bacteria, fungi, and algae also act upon the nutrients released into the water by the decomposing organic material from these plants. Plants (known collectively to science as macrophytes) grow in or near water and are either emergent, submergent, or floating, and play a role in "filtering" these flooded habitats in nature.

Many, like the plants in the pic below, are simply terrestrial grasses which have adapted to survival under water for extended periods of time. This adds to the diversity of materials- both living and dead- in these compelling habitats.

A most interesting combination of elements, indeed.

A most compelling model.

A most fascinating example of a "functionally aesthetic" environment that you can duplicate in your home aquarium. Think about the environment, its external influences, the conditions, and the life forms that make use of it the next time you're conjuring up ideas for a new tank...It just might help you create one of the most amazing aquariums you've ever built!

Stay studious. Stay inspired. Stay curious. Stay excited. Stay diligent...

And Stay Wet.


Scott Fellman

Tannin Aquatics  

August 07, 2020


Life on many levels...

As a lifelong hobbyist, I've kept thousands of fishes in many dozens of aquariums over the years. Many of them were dedicated to single species, yet many more were evolved as so called "community aquariums", filled with a variety of fishes and plants.

What strikes me most about many community aquariums is their refreshing diversity. They feature a complete range of life forms, such as fishes, plants, and even invertebrates. These aquariums are rich with life, and make no apologies for the wide-ranging selection of fishes and the complex growth of plants. 

Just like in Nature, these systems incorporate life forms that provide beneficial "collateral benefits" for their inhabitants, such as food, shelter, and nutrient export.  Well-stocked community aquariums are beautiful systems that are a visual delight, affording many opportunities to see examples of the endless variety of aquatic life forms.

We can learn a lot from diverse community aquariums. Yet, we can take it a little further. 

Typical aquairums- community or otherwise- generally  don't focus on the "small stuff"- the life forms like microorganisms, small crustaceans, worms, etc. A large community of small creatures- all which contribute to the health and stability of the closed aquatic ecosystem.


There is a lesson there...something that we all know, but something that we likely don't consciously think about. That is, the idea of closed aquatic systems as microcosms. A microcosm is defined as "A community, place, or situation regarded as encapsulating in miniature the characteristic qualities or features of something much larger."

Like, ya' know- a miniature version of a natural habitat.

Something that we often aspire to in aquariums. However, something that I feel we often create on the most superficial of levels. I mean, we add fishes, and we add plants...but we kind of stop it there, right?

What about facilitating the existence of life forms at a variety of levels? Like, starting with the bacteria and other microorganisms which make up the miniature ecosystem we're trying to create? Why not create an environment which is supportive of life on many levels?

That's the whole idea...

And of course, these organisms and their processes create not only the basis of a food web, but the development of an entire community of co-dependant organisms which work together to process nutrients and support life forms all along the chain. When we encourage, rather than remove these organisms when they appear, we're helping perpetuate these processes.

I can't stress how important it is to let these various organisms multiply.

And we need to think about our relationship with detritus, decomposing botanical materials, and sediments in our tanks.

Yes, I'm asking you to not only "leave them be" -but to encourage their accumulation, to foster the development and prosperity of the organisms which "work" them. 


Now, again, I have to at least ask the rather long question, "Are these things (detritus; decomposing materials) really problematic for a well-managed aquarium? Or, do they constitute an essential component of a closed aquatic ecosystem...One which can actually provide some benefits (ie; supplemental nutrition) for the resident fishes and the community of life forms which support them?"

Many of us have already made a mental shift which accepts the transient, subtle beauty of decomposing botanical materials, tinted water, biofilms, and the like, so it goes without saying that taking it a little further and allowing these materials to completely breakdown to serve as the substrate for our aquatic ecodivesity is simply the next iteration in the management of blackwater/brackish botanical-style aquariums.

So, yeah- there IS a lot to consider when utilizing botanical materials in your aquarium. It's far, far beyond the idea of just "dumping and praying" that has been an unfortunate "model" for how to utilize them in our aquariums for many years. It's more than just aesthetics alone...the "functional aesthetic" mindset- accepting the look and the biological processes which occur when terrestrial materials break down in our tanks is a fundamental shift in thinking.

By studying and encouraging the growth of this diversity of organisms, and creating a multi-faceted microcosm of life in our tanks,  I believe that we are contributing to an exciting progression of the art and science of aquarium keeping!

It's all about life...on many different levels.

Think about that.

Stay curious. Stay engaged Stay excited. Stay patient. Stay diligent...

And Stay Wet.


Scott Fellman

Tannin Aquatics


August 05, 2020


An idea that's been floating around in my head...

As we go further and further into the world of botanical-style aquariums; deeper into unusual niches and ideas, it's refreshing and inspiring to turn towards our mentor, Nature- to find out how to replicate them in the aquarium.

You're probably either mildly amused, or completely fed up fed up with our obsession about leaf litter in aquariums, or maybe- just maybe- just as geeked-out as we are about 'em, right?

Yeah, I kinda figured it'd go down something like that.

We make it a point to scour scientific papers and scholarly research articles for topics relevant to our obsession. The other day, I stumbled on a cool paper about...floating leaf litter banks!

Fascinating natural aquatic structures found in Amazonia, which are extremely enticing!

(Photo from Carvalho, et al.)*

Oh, you know where this is going...

So imagine, if you will, a "classic" submerged leaf litter bed in Amazonia, composed of a variety of leaves, branches, twigs, seed pods, and other botanical materials...yet floating on the surface of the water! What you get is a fairly deep layer of plant materials colonized by fishes and other creatures, which forage on the macro invertebrate life and insects found in these assemblages. Biologists call this an "ephemeral" habitat, as it is transitory or temporary as it slowly breaks apart. 

Okay, so it slowly breaks apart over months and months...or maybe longer. Yet it's not permanent...

According to one study I read, eventually, most of the organic debris is deposited on the stream bottom or drifts downstream until it becomes trapped by a variety of natural obstacles.

These floating, or partially submerged litter beds either accumulate on tree branches hanging from the riparian vegetation, or they remain anchored by fallen tree trunks and branches near the water surface, where they may form a really deep layer of materials.

After reading about these assemblages, I found this to be an irresistible niche habitat to replicate in the aquarium! It seems to be the freshwater analog of the Sargassum "forests" of the Caribbean and Tropical West Atlantic! Little oases of life in the vast, open water.

According to one study, these floating or partially submerged leaf litter banks either accumulate among the branches of riverside vegetation during the high water season, gradually floating downstream, or stay anchored in place by fallen tree trunks and other large materials, ultimately forming a more "traditional" submerged leaf litter bed.

It was discovered that many fish species associate with these floating litter banks for the entire wet season, and one of the reasons they stay put is because their food sources are there, too! In fact, a species of "water bug", Weberiella rhomboides, is found almost exclusively in these floating banks, attracting large numbers of insectivorous fishes, like characins, catfishes, knifefishes, and others. 

In other words, these stands of floating leaves and botanicals are literally a "moveable feast", a veritable "floating fish buffet", if you will! The fish populations found in these environments are typical of what you'd expect to find in a more "static" leaf litter environment.

What fishes would you expect to find in this cool niche? Well, it's kind of a "who's who" of blackwater, leaf litter zone dwellers, some of which are very familiar to us as hobbyists- for example, characins like Hemmigramus species, Moenkhausia species, the killifish Rivulus ornatus, and of course, cichlids, including a number of ApistogrammaCrenicichla, Hypselecara, and the much-loved Mesonauta festivus, to name a few. 

And then there is that most ubiquitous of leaf-litter-dwelling which I've almost never seen in the hobby, but I see everywhere in leaf litter population studies, Elachocharax pulcher! I've been told that it shows up occasionally, but being a leaf litter dweller, it probably evades capture by local fishers, and it's cryptic coloration makes it less than exciting (read that, fucking dull) for any but the most geeked-out me and, hopefully, you!

Okay, rad. Lots of fish choices...That was never the issue, right?

The bigger next question is, how the hell would you recreate a facsimile of this environment in an aquarium? (second only to, "Would you want to?")

The answer is, "Of course!"

Now, I admit I haven't tried this idea myself yet, but being such an enabler, I want to encourage someone with an extra tank and a healthy fascination with this type of niche to try it if I don't get to it first!

Just how would you do this? Well, I envision the process as pretty straightforward. I'd personally employ a wide aquarium, for a nice sense of perspective. Likely a "standard" height or deeper. I'd utilize a substrate of fine sand, with a smattering of twigs (like oak twigs) and some smaller leaves, like Yellow Mangrove.


And of course, I'd use some leaves for the surface. I'd select a bunch of smaller leaves, like Guava, Yellow Mangrove, and a smattering of Live Oak leaves, with a few twigs thrown in for good measure.

Of course, we'd recommend a little prep- perhaps just a few minutes of steeping in boiling water- or just pour over some boiling water to help clean them and perhaps just soften the outer cuticle layers. The idea is not to saturate them to the point where thy'll sink right off the bat, but to at least give them a good cleaning. 

And of course, they'll float for a while, until they're completely saturated.

Ohh, this is getting really good...

I'd imagine that you'd probably filter this tank with an outside power filter or canister filter with the return positioned in such a way as to minimally disturb the surface. You'd essentially be creating a diverse assemblage of leaves, just like you would if you were doing a "conventional" leaf-litter display (Ha! I love that- a "conventional leaf litter display"- look how far we've come...). 

Now, eventually, some of this stuff would sink, or be trapped below the floating "matrix", and you'd end up with materials on the!  It would transition naturally to a more common "botanicals-on-the-bottom" display. So this is essentially an "ephemeral display"- transitioning from a "floating leaf litter bed" to a submerged leaf litter aquarium! Or is it a "transitional ephemeral display?" 

Whatever you want to call it- it's an amazing idea for an aquarium, I think.

Twigs, leaves, flowers, terrestrial and floating aquatic plants...Nature provides no shortage of inspiring features to incorporate into such a display.

Of course, you could probably keep it going by replacing the leaves and such as you would anyways, right? And as the wood becomes submerged, you'd "let it do it's thing", and/or replace/add new pieces.

I would wager that no one has ever really tried this in an aquarium before- at least, not intentionally. If you have, I would love to see it! If you haven't, I'd love to see you do it!

Shit, now I'm convincing myself to do it!

I do have an empty tank lying around...

Imagine the possibilities with a display like this? I sure can!

Stay creative. Stay excited. Stay resourceful. Stay inspired...

And Stay Wet.


Scott Fellman

Tannin Aquatics  



August 04, 2020


Looks aren't deceiving- botanical-style aquariums ARE a different "breed!"

The botanical-style aquarium is a little bit different than the typical approach to aquarium-keeping. Not only because they simply look different- but the fact that they rely on biological processes which we have often not given much thought to, other than a bit of apprehension over them.

Of all these processes, none is mentioned more frequently- or with as much reverence around these parts- as the process of decomposition. Yeah, you're actually hearing about a fish geek celebrating this- finding something compelling, fascinating, and fundamental about stuff breaking down in our tanks.

Decomposition, to refresh your memory, is the process by which organic materials are broken down into more simple organic matter. For our purposes, we are primarily interested in the breakdown of plant matter, ie; botanicals and leaves. It is in part responsible for some of the unique habitats that we love so much-and an inspiration for some unique aquariums with previously unappreciated aesthetics!

We can look at natural aquatic systems for inspiration and clues about how these systems are "powered" by an influx of botanical materials- specifically, leaves.

When leaves enter tropical streams and other bodies of water, fungal colonization increases the nitrogen content (because of fungal biomass) and causes leaf maceration. This is known by aquatic ecologists to be evidence of microbial colonization. There are many different stages in the process, starting with the leaching of materials from the cells of the botanicals during initial submersion, in which soluble carbon compounds are liberated in the process. A rapid release of phosphorus accompanies this leaching.

Of course, the process ultimately leads to physical breakdown and/or fragmentation of the leaves and botanicals into smaller "pieces", which possess larger amounts of surface area for microbial attachment.  Extensive ecological studies done by scientists specifically in regard to leaf litter have yielded a lot of information about this process.

The fungi known as aquatic hyphomycetes produce enzymes which cause leaf maceration, and in as little as 2 to 3 weeks, as much as 15% of the decomposing leaf biomass in many aquatic habitats is processed by fungi, according to one study I found.

In experiments carried out by aquatic ecologists in tropical forests in Venezuela, decomposition rates were really fast, with 50% of leaf mass loss in streams occurring in less than 10 days!

The ultimate result is the transformation of what ecologists call "coarse particulate organic matter" (C.P.O.M.) into "fine particulate organic matter" (F.P.O.M.), which may constitute an important food source for other organisms we call “deposit feeders” (aquatic animals that feed on small pieces of organic matter that have drifted down through the water and settled on the substrate) and “filter feeders” (animals that feed by straining suspended organic matter and small food particles from water).

And yeah, insect larvae, fishes and shrimp help with this process by grazing among or feeding directly upon the decomposing botanical materials. So-called "shredder" invertebrates  (shrimps, etc.) are also involved in the physical aspects of leaf litter breakdown.

So, there's a lot of supplemental food production that goes on in leaf litter beds and other aggregations of decomposing botanical materials. It's yet another reason why we feel that aquariums fostering significant beds of leaves and botanicals offer many advantages for the fishes which reside in them! 

The biggest allies we have in the process of decomposition of our botanicals in the aquarium are microbes (bacteria, fungi, and protozoa, specifically). Ecologists will tell you that during the early decay phase of botanicals/leaves, the leaching of water-soluble substances plays a key role in the loss of the physical mass of these materials.

Alteration of the botanicals is done chemically via this microbial action; ultimately, the components within the botanicals/leaves (lignin, cellulose, etc.) are broken down near completely. In aquatic environments, photosynthetic production of oxygen ceases in submerged terrestrial plants and their parts, and organic matter and nutrients are released back into the aquatic environment.

Fungal colonization facilitates the access of invertebrates to the energy trapped in deciduous leaves and other botanical materials found in tropical streams. Bacteria and fungi that decompose decaying plant material in turn consume dissolved oxygen for respiration during the process.

This is why adding too much botanical material too rapidly to an aquarium can create big problems for the fishes! A rapid decrease in dissolved oxygen in a small body of water can be disastrous; or, at the very least, leave fishes gasping at the surface! And of course, that's why we tell you to deploy massive patience and to go slowly when adding botanicals to an established aquarium...

Now, I'm just one guy, but I personally haven't had issues with the complete decomposition of botanicals and leaves being left to accumulate in my aquariums. In almost three decades of playing with this stuff, and being a hardcore, water-quality-testing reef keeper during much of that time, I can't ever, EVER recall I time where the decline of a system I maintained could be pinned specifically on the detritus from decomposing botanical materials as a causative factor in reducing water quality.

In fact, I have never had a situation where water quality has been an issue in a tank not performing well. And I suspect- neither have many of you.

Okay, put me in for a medal, right? 

That's not the point.

What I'm getting at is that I have always been a firm believer in some forms of nutrient export being employed in every single tank I maintain. Typically, it's regular water exchanges. Not "when I think about it', or "periodically", mind you.

Nope, it's weekly. 

Now, I'm not saying that you can essentially disobey all the common sense husbandry practices we've come to know and love in the hobby (like not overcrowding/overfeeding, etc.) and just change the water weekly and everything's good.

Water exchanges are helpful. However, they're not a panacea for all of the potential "ills" of a poorly managed tank.

What I am saying is that incorporating regular water exchanges into your system gives you the ability to dilute any potential accumulating organics/pollutants before they become a significant negative ve impact on water quality.

They simply give you a bit of a "buffer", essentially.

I don't need to go into the well-trodden reasons about what water exchanges are a good thing in the aquarium. However, I do need to give us a collective whack upside the head and encourage each and every one of us to think about this stuff from the perspective of an overall closed ecosystem. Think about what the nitrogen cycle is and does, and think about the impact of inputs and exports into and out of our closed systems. 

Pretty much everything we do in a botanical-style blackwater aquarium has a "natural analog" to it! 

Some hobbyists have commented that, as their leaves and botanicals break down  the scape as initially presented changes significantly over time. Wether they know it or not, they are grasping "Wabi-Sabi"...sort of.

("Again, Fellman?" Yes. This concept is really important!)

One must appreciate the beauty at various phases to really grasp the concept and appreciate it. To find little vignettes- little moments- of fleeting beauty that need not be permanent to enjoy.

And, despite their transience, these materials function as diverse harbors of life, ranging from fungal and biofilm mats, to algae, to micro crustaceans and even epiphytic plants. Decomposing leaves, seed pods, and tree branches make up the substrate for a complex web of life which helps the fishes that we're so fascinated by flourish.

And, if you look at them objectively and carefully, these assemblages-and the processes which form them- are beautiful- both in Nature and in the aquarium!

One need only study the wild aquatic systems of the world to realize that it's not all "crystal clear and sterile" out there- and that our aquariums in all of their tinted, murky glory, filled with fungal growth and decomposing materials- will reflect this.

Nature "calls the shots" here.

And that it's totally okay.

We are not managing botanical-style aquariums to be sterile glass boxes, "dioramas", or "zen gardens." It's not just a "look."

We are understanding that a real "nature/natural-style aquarium" embraces the processes of nutrient import/export, decomposition, bacteria/fungal growth, and long-term nutrient utilization by the organisms which we keep. The appearance is far different than a system strictly set up for aesthetics. Rather, our systems offer a unique combination of form AND function...what we call "functional aesthetics."

The "look" and the "function"- working hand in hand to create a replication of Nature far more authentic than what we've done in the past in the hobby. And what is required to execute this?

Patience. A long-term view. Observation. Understanding.

Embrace all of these things...and grow from the process.

Stay curious. Stay diligent. Stay involved. Stay brave...

And Stay Wet.


Scott Fellman

Tannin Aquatics 



August 03, 2020


The waiting game...part of the journey.

Every aquarium is a unique microcosm, with different looks, goals, and processes that it embraces. These things depend upon a variety of environmental inputs, internal processes, and external and internal influences- such as the organisms within the system. They take time to evolve, stabilize, and flourish. We talk about this incessantly, I know...but it's the whole game when it comes to botanical-style aquariums!

Botanical style aquariums are not "static diorama" aquascapes...They're not "all done"  or "ready for judging" (gulp) as soon as the last seed pod is placed. In fact, that's just the very beginning of a long and continuous process.

They are systems which evolve.

They have to in order to become what they must. And this doesn't happen immediately. These tanks simply need time. They need to "breathe" (metaphorically speaking) and be left to do what Nature intends for them to do.

A recent example is my brackish water aquarium, which took over a year, really to evolve into something exactly like I envisioned...It simply wasn't "there" after a month or two, or even six. Our botanical-style tanks, with few exceptions- just don't start looking their best- all "earthy" and "funky" and...established- for a few months, typically.  

To terminate them "mid-evolution" because they don't look the way you want them to is really a kind of shame! And it overlooks the very important part: Botanical-style aquariums are not an "aquascaping style"- they are a methodology which embraces natural materials and processes to "finish" what we start- to not only help create and enrich the ecosystem- but to change the aesthetics as it does.

Of course, there are a few things you could do to sort of "expedite" the "established" look of a botanical-style tank, but they're really just sort of "hacks" (ugh I hate that word!)- and are no substitutes for just letting a tank evolve over time naturally.

"Well, what are they, Fellman?" 

So you could use some botanicals and partially decomposed leaf litter, substrate, and even water from an established botanical-style tank to give you a bit more of an "evolved" vibe and definitely some microbial populations and therefor, some function.

And, if doing this for purely "functional" reasons as opposed to just trying to "hack" the "look"- I can actually see tremendous merit to this idea. Hell, adding sand or gravel from an established tank to "jump-start" a new one has been standard practice in marine aquariums for decades, and in freshwater as well.

Doing this with botanical materials- rich with detritus, biofilms, fungal growth, and beneficial bacteria- is simply the botanical-style version of this time-honored process, right? And it makes perfect sense.

Yet, there is no substitute for patience and the passage of time.

Looking back on some of my favorite tanks that I've executed in the past few years, it becomes increasingly obvious to all that these systems really don't hit that "look and feel" that we expect until long after they have evolved naturally...however long that is.

Stuff needs to acquire a "patina" of biofilm, a "stain" from the tannins, and decomposition of botanical materials needs to really begin before one of these systems turns "functional" as well.

I mean, every new botanical-style tank looks cool from day one...A lot of people love the clean and fresh-looking leaves, and seed pods that are squeaky clean. But the long-established systems are the ones that stand out.

After 6 months, that's when things get really special.

That's when the bulk of the "settling in" is done. The bacterial, fungal, and microorganism populations have increased, and nutrient imports and exports have balanced out and stabilized. The tank looks great, smells earthy and pleasant, and the fishes take on a very relaxed demeanor.

I've long held that my fave botanical-style, blackwater aquarium of all was the one I did about 3 years aquarium utilizing mangrove wood, extensive leaf litter, and catappa bark throughout. This is probably the only tank in recent years that I've truly regretted changing and moving on from! 😂 

And it wasn't all sexy and dark and established-looking from the get-go.


It literally looked like shit for the first couple of months of it's existence: Slightly tinted water, a contrived-looking "campfire-like" wood stack, bare sand, and mostly intact botanical materials. I had to do a bunch of iterations with the hardscape to get it where I wanted it. It almost looked contrived, but I knew from experience that if I waited it out, let Nature do Her thing- that the potential was huge in this tank.


However, a few months in, biofilms started forming. The wood acquired that "patina" we talk about so much. Leaves and botanicals broke down...And the water took on the most earthy-looking, deeply mysterious color I've seen in a blackwater aquarium. A very slight "turbidity" or "flavor" as one of my friends called it- that was as compelling as it was beautiful.

Yeah, by some standards, the water in the tank could be described as almost "turbid"- taking on an appearance as though there were fine materials in the water column. Yet, the tank had a real magical appearance with the LED lighting; the fishes were as colorful, relaxed and happy as any I've ever seen, and the water parameters were spot-on and consistent for as long as the tank was set up. IN fact, I had three spawns of Rummy Nose Tetras in that tank!

This tank had a certain "something":

The essence "wabi-sabi", for sure. Transience, the ephemeral aspects of our botanicals...the wonders of Nature, embraced.

Now sure, there are some concepts which have the "broken-in" look from almost day one, simply by virtue of the materials which they utilize. An example was the "pure leaf litter" aquarium which I set up to test the idea of internally-sustainable food production for fishes. The system was set up with about a 2"/5.08cm layer of Live Oak Leaf Litter and Yellow Mangrove Leaves  to comprise the entire "hardscape" of the aquarium.

Yeah, it was essentially "finished" from day one- at least, aesthetic-wise. And yet, it only improved over time in ways I can't really explain.

A shoal of Paracheirodon simulans (the "Green Neon Tetra") formed the perfect "subject" for this concept tank. Once out of quarantine, the fishes were not fed at all in this aquarium, and almost doubled in size in a couple of months! It didn't take all that long for the aquarium to acquire the "look" of a very long-established one, thanks to the capability of the Live Oak leaf litter to acquire biofilms and some detritus. 

Now, this tank was certainly not one that everyone would find "attractive"- however, to a botanical-style/blackwater aquarium freak like me, this aquarium was more than just a "proof of concept"- it was an example of an unconventional aquarium that was able to sustain its residents for the duration of the experiment. Oh, and they spawned! Twice! I think that this tank could have ran for an indefinite period of time, with only routine maintenance and replenishment of leaves as necessary.

There was a certain beauty to that "no scape", as one of my reefkeeping friends called it. And yet, it took a bit of time to REALLY get the perfect look. A "waiting game" of sorts. 

Some botanical-style aquariums are simple in concept, look "about right" from day one; and you just need to set them up and sort of "wait it out" until they start looking more "established"- which might only take a few weeks or a month or two at the most. A perfect example is the tank I've affectionately called the "Tucano Tangle"- an aquarium set up to replicate part of the habitat of the Tucano Tetra, Tucanoichthys tucano.

Possibly one of the easiest biotope-inspired aquariums I've ever set up, this one really took on the "look" I was trying to achieve in seemingly little time at all. It started with a simple "superstructure" of Spider Wood, topped with several specimens of Melastoma Root (don't worry, we have more coming in a few weeks....) to achieve as sort of tangled, earthy, "deep" sort of look. The substrate was a very shallow mix of sand and some very fine claylike materials, topped with a sprinkling of (wait for it) Live Oak leaf litter.

After an initial settling-in phase, this tank easily shifted out of "new and pristine mode" into "looks like a natural habitat" mode, as I kind of expected that it would!

As the water darkened, and the biofilms and "patina" took over, the tank became a perfect demonstration of the power of simply "executing and waiting" on your tank to "do its thing" and evolve.

And evolve it did, in a relatively short period of time!

Now, other experimental systems I've played with simply take more time to do their thing and come into their own before you'd really move on.

However, they actually are intended for "forced iteration"- a deliberate change to their composition or progression. Indeed, after the initial setup, the "evolved" product looks little like what it started out as. Of course, these projects may take many months to evolve as part of the plan. The "Urban Igapo" tanks I've shared with you are good examples of this.

These tanks are what you could call "continuously evolving" systems. They change from terrestrial to aquatic and back over time. You just sort of keep them going by inundating them, emptying them, and repeating the process.

I know. I know. This isn't exactly earth-shattering. 

On the other hand, in the world of the botanical-style aquarium, the idea of leaving the substrate and leaf litter/botanical "bed" intact as you "remodel" isn't exactly a crazy one. And conceptually, it's sort of replicates what occurs in Nature, doesn't it?

Yeah, it DOES.

Think about this for just a second.

As we almost constantly discuss, habitats like flooded forests, meadows, vernal pools, igarape, and swollen streams tend to encompass terrestrial habitats, or go through phases where they are terrestrial habitats for a good part of the year.

In these wild habitats, the leaves, branches, soils, and other botanical materials remain in place, or are added to by dynamic, seasonal processes. For the most part, the soil, branches, and a fair amount of the more "durable" seed pods and such remain present during both phases.

The formerly terrestrial physical environment is now transformed into an earthy, twisted, incredibly rich aquatic habitat, which fishes have evolved over eons to live in and utilize for food, protection, and complex, protected spawning areas. 

All of the botanical material-shrubs, grasses, fallen leaves, branches, seed pods, and such, is suddenly submerged; often, currents re-distribute the leaves and seed pods and branches into little pockets and "stands", affecting the (now underwater) "topography" of the landscape.

Leaves begin to accumulate. Detritus settles.

Soils dissolve their chemical constituents- tannins, and humic acids- into the water, enriching it. Fungi and micororganisms begin to feed on and break down the materials. Biofilms form, crustaceans multiply rapidly. Fishes are able to find new food sources; new hiding areas to spawn.

Life flourishes.

And it is part of a sequence. A pattern...A journey. Perhaps what could best be called an evolution- which Nature has carefully set up and managed over eons. 

In our own aquarium work, we can replicate this sequence and's not that hard to do. The really difficult part is the waiting. Acquiring the patience that we must deploy as we watch our aquariums evolve, uninterrupted- under the steady hand of Nature.

That's the magic.

It's a process- the part of the journey which every botanical-style aquarist needs to embrace and understand.

Of course, an aquarium which utilizes botanicals as a good part of its hardscape follows a set of phases, too. And I've found that once a botanical-style aquarium (blackwater or brackish) hits that sort of "stable mode", it's just that- stable. You won't see wildly fluctuating pH levels, increasing nitrates, phosphates, etc. To a certain degree, the aquarium has achieved some sort of "biological equilibrium."

Now, one thing that's unique about the botanical-style approach is that we tend to accept the idea of decomposing materials accumulating in our systems. We understand that they act, to a certain extent, as "fuel" for the micro and macrofauna which reside in the aquarium. The idea of leaving this material in place over the long-term is a crucial component of this approach, IMHO.

When we do that- when we make those mental shifts and accept that our aquariums aren't really "finished" in 5 days- or 50- we have suddenly begun to understand this whole "botanical-style aquarium thing."

It's a dynamic that needs to be understood, embraced, and celebrated. It's what separates the work we do and the tanks that we love from the rest of what's common in the hobby. It's a challenge, of course. Yet, it's perhaps its one of the the most rewarding ones we can take on in the aquarium hobby.

It starts with patience, and continues with a "waiting game." Yet, an enjoyable one, nonetheless.

Stay patient. Stay studious. Stay grounded. Stay diligent...

And Stay Wet.


Scott Fellman

Tannin Aquatics 




August 02, 2020


Who eats what...and where? Thoughts on embracing "the whole picture" of our fishes' natural habitats in our aquariums.

Today's installment is one of those sort of meandering, perhaps choppy amalgamations of ideas, cobbled together with my typical fish-geek enthusiasm; heavy on facts, and heavier on pontificiation and speculation! 

However, I think you might like this. It's a sort of summary of what's been on my mind lately about botanical-style aquariums.

As you know, I’m pretty much an uber nerd about almost any arcane aquarium related subject. And of course, part of my regular “course of study” takes me well outside of the aquarium world. In fact, most of the best insights I have obtained on tropical fishes and the environments from which they come are derived from scholarly articles.

And these scholarly articles can give you a ton of information about not only the fishes- but about the environments from which they come. And when we combine this information with what we already know from our experience with keeping them in aquariums, the possibilities to refine our work to create more unique, imaginative, and "functionally aesthetic" aquatic displays are too numerous to mention.

I think that we as aquarists should investigate more carefully and thoughtfully some of the more subtle, yet potentially very important characteristics of the habitats from which our fishes come. Stuff which we may not have thought much about previously- like the turbidity of the water, the density and composition of the substrate, and the amount of water movement in a given habitat.

Did you catch that last one? Many fishes are found in specific types of water-movement-dynmaic habitats. There are two main classifications:

Lentic ecosystemswhich are stationary or relatively still water habitats, and Lotic ecosystems, which involve flowing waters, such as streams and rivers... Lentic ecosystems are usually habitats such as ponds, lakes, pools, and wetlands. Liek those flooded Pantanal meadows and flooded forests which we obsess over around here!

Again, when you're looking at the environments from which our fishes come from in a wholistic sense, you start thinking about more than stuff like the abundance of branches, rocks, leaves, and stuff like that. You start thinking about the composition of the substrates, the color and or turbidity of the water, and other factors which we as aquarists likely haven't paid as much attention to over the past century.

There is so much you can learn by diving deeper and detaching yourself from thinking about stuff fro ma hobby perspective for just a bit.

For example, I love reading about the dietary preferences of many of the fishes we keep- or wish to keep- in our botanical-style/blackwater aquariums. Why? Well, for one thing, when you know what the fishes eat, you get a good picture of how they live- and where!

Interestingly, many of my fave fishes (characins and other small guys) have diets which consist largely of stuff like “insect larvae, sponges, Bryozoa, algae and detritus”- all items which are found in their preferred environments... and in botanical- style aquariums, right?


I think it's important that we look at our botanical-style aquariums not just as some unique aquascape- which, of course, they are- but as a closed microcosm- a miniature environment featuring a variety of organisms all interacting with each other in a manner which can benefit the system as a whole. If we assemble our system based on this kind of thinking, the possibilities for creating a more functional habitat is increased.

And it often starts with food.

Feeding is a fundamental part of the life of our fishes, and it literally determines who lives where, and how. And examining the diets of our fishes can give us amazing clues about how to design a more appropriate and functionally realistic aquatic habitat for them, can't it?

Of course!

So, the idea here is that setting up a botanical-style aquarium can be based around not only the environmental requirements of your target fishes (ie; water chemistry, temperature, light intensity, and physical surroundings)- it can be built around other factors, such as the availability of food sources.

If you look at some specific types or families of fishes, you can get an idea of where they live by considering what they eat.

For example, some of my fave fishes, the Pencilfishes, have very specific dietary preferences- and this dictates not only where they live, but how they live in the water column of their habitats. Pyrrhulina feed on insects, and inhabit the upper portion of the water column. Fishes in the genus Nannostomus feed on benthic invertebrates, and tend to live lower down in the water column.

And then there are those other guys...

Everyone knows about the Piranha and it’s penchant for eating flesh of other fishes. It’s relatives in the family Serrasalmidae, Colossomoa, Metynnis, and Piractus, consume a more herbivorous diet, like fruits, seeds, leaves, and occasionally, flowers. Some species only consume the whole fruits, defecating large numbers of seeds in the process—functioning as highly effective seed dispersers for wide range of trees in the flood plains which they inhabit. 

This is fascinating. These fishes are an integral part of the habitats in which they reside- and they help shape the future of it with their eating habits!

Some are so specialized that they forage almost exclusively on aquatic plants (such as plants in the family Podostemaceae) and consume the leaves, seeds, and flowers of these plants! 

Interestingly, the whole group is very sensitive to noise and splashing in the waters where they live. Piranhas respond to the noise thinking that there are animals or fish prey around, where the frugivores, like Colossoma hear a splash and think, “Ahah! a fruit just fell into the water!” ( okay, they may not THINK that, but they do respond to the noise looking for fruits!

Some in the family, such as Myloseoma, feed on all sorts of stuff as they can find it, ranging from seeds, fruits, flowers, and algae to stuff like spiders, cockroaches, beetles, and ants. They’re even known to eat monkey feces! Okay, I'll leave that one alone- but you get the idea...they're hardly picky, right?

I mean, monkey shit? Yeah.

Durophagous fish eat hard shelled or exoskeleton bearing organisms- crabs, mussels, snails, etc. Usually, these kinds of fishes are found in lakes or larger rivers, where water conditions and flow characteristics tend to favor the presence of those food sources.

And of course, fishes often move throughout their habitats seasonally, following the food. 

A few of my favorite fishes, such as the awesome Crenuhus spilurus, the "Sailfin Tetra"- have broad dietary preferences. It's been observed that the fish feed freely during daylight hours, and grab most of their food as it falls though the water column. What do they eat? Well, this is interesting to me: A lot of particulate matter that sinks; specifically, stuff like fruits, terrestrial insects, and very young tadpoles made uo the bulk of the stomach contents in a recent (2016) study of this fish.

So, yeah, a typical consumer of...allochthonous materials (stuff which comes from the environment surrounding the aquatic habitat)!

Now, we've talked extensively in several blog posts over the past couple of years about the idea of allochthonous input (literally, food from the sky, lol) and how it impacts the feeding habits of many fishes, as well as their social and behavioral habits, and what could loosely be referred to as their "migratory patterns."

It's long been known that fishes which inhabit the flooded forest floors (igapo) of Amazonia, for example, tend to literally "follow the food" and move into new areas where greater feeding opportunities exist, and will even adjust their dietary preferences seasonally to accommodate the available foods.

In this instance, it typically means areas of the forest where overhanging vegetation offers falling peices of fruit, seeds, nuts, plant parts, and the occasional clumsy insect, like an ant, which falls from the branches of said vegetation. So, here is where the idea gets interesting to me: Wouldn't it make a lot of sense to create a biotope-style aquarium which not only represents the appearance of the habitat, but also replicates, to a certain extent, the function of it?

Of course it would!  (Surely, you wouldn't have expected any other answer from me, right?)

In this case, the "function" being the presence of allochthonous materials! Well, yeah. we've just described our botanical-style aquariums in (pardon the expression) a nutshell! Our tanks are replete with lots of terrestrial plant material (ie; botanicals, leaves, and wood), upon which our fishes and other aquatic animals will forage and even consume them directly over time.

I asked myself which materials would most realistically represent some of these items, and sort of came up with a list of my personal favorites. Now, obviously, you can utilize other stuff- and in terms of actual foods, you might even want to experiment with little appropriately-sized bits of fruit for fishes to consume directly! (back to that shortly)


Here are the botanicals that I think would best serve to represent some of the allochthonous materials we see in these forests:

Dysoxylum pods

Calotropis pods

Banana Stem Pieces

Pyrifolium pods

So, yeah, you could add an assortment of these and/or other materials to your tank, with the sole intention of utilizing them to represent the materials which fall off the trees and are directly consumed by some fishes and shrimp. Because of their physical structure, these selections tend to soften up fairly quickly after submersion, and are also pretty good at "recruiting" biofilms, which serve as a significant supplemental food source for a variety of fishes.

Utilizing appropriate fruits like finely-chopped açaí berries, blueberries, strawberries, Passion Fruit, and bananas to represent the fruits of the forest, is something I've played with for a long time with my Tetras and other characins. Believe it or not, they'll actually consume these foods directly, and I've also used flax seed and chia seeds for this purpose as well. 

Passion Fruit ( Image by fir0002   Used under GFDL 1.2)

Many of these will represent the fruits of the Amazon rain forest, such as Camu Camu, Cupuaçu, Passion Fruit, aguaje (fruit of the Mauritia Plam), If you search health food stores and speciality fruit/produce vendors, you might find fresh or packaged versions of some of these unique fruits, or you could use the more commonly available substitutes mentioned above.

I could imagine changing up the diet of your fishes seasonally, along with ideas like environmental manipulations and "power dosing" botanicals into the aquarium to represent the "high water" season, to see how this impacts behavior, health, and spawning activities of your fishes from this habitat. We have the technology. We have the knowledge...and we have the food!

Studies of blackwater communities showed that, during these cycles, a greater diversity of fishes exists there. Many species were found to be specialized feeders. Fish, detritus and insects were the most important food resources supporting the fish community in both high and low water seasons, but the proportions of fruits, invertebrates and fish were reduced during the low water season.

Are there some "takeaways" here for us fish geeks?

Hmm, what this means to us is that fish sort of "follow the food", right? And that the "seasonal availability" of some food sources actually dictates overall fish behavior. 

And then, there's our old friend...detritus. 

"detritus is dead particulate organic matter. It typically includes the bodies or fragments of dead organisms, as well as fecal material. Detritus is typically colonized by communities of microorganisms which act to decompose or remineralize the material." (Source: The Aquarium Wiki)

Shit, really?

It's one of our most commonly used aquarium terms...and one which, well, quite frankly, sends shivers down the spine of many aquarium hobbyists. And judging from that definition, it sounds like something you absolutely want to avoid having in your system at all costs. I mean, "dead organisms" and "fecal material" is not everyone's idea of a good time, ya know?

Yet, when you really think about it, "detritus" is an important part of the aquatic ecosystem, providing "fuel" for microorganisms and fungi at the base of the food chain in tropical streams. In fact, in natural blackwater systems, the food inputs into the water are channeled by decomposers, like fungi, which act upon leaves and other organic materials in the water to break them down. 

And the leaf litter "community" of fishes, insects, fungi, and microorganisms is really important to these systems, as it assimilates terrestrial material into the blackwater aquatic system, and acts to reduce the loss of nutrients to the forest which would inevitably occur if all the material which fell into the streams was washed downstream!

That sounds all well and good and grandiose, but what are the implications of these processes- and the resultant detritus- for the closed aquarium system?

Well first off, let's admit that the stuff  just doesn't look that nice to most of us, and that's partially why the recommendation for a good part of the century or so we've kept aquariums is to siphon it the hell out! And that's good advice from an aesthetic standpoint- and for that matter, from a husbandry standpoint, as well.Excessive amounts of accumulating waste materials can lead to increased phosphate, nitrate, and other problems, including blooms of nuisance algae.

Emphasis on the word "excessive" here...(which begs the question, "What is "excessive" in this context, anyways?)

Most hobbyists don't have the time, inclination, or optimized system set up to take advantage of a small accumulation of this stuff. However, with the importance of detritus in creating food webs in wild leaf litter communities, which we are now replicating in aquariums, could there actually be some benefit to allowing a little of this stuff to accumulate? Or at least, not "freaking out" and removing every single microgram of detritus as soon as it appears?

I think so. Really.

Is this another one of those long-held "aquarium truisms" that, for 90% of what we do is absolutely the correct way to manage our tanks, but which, for a small percentage of aquarists with the means, curiosity and inclination to experiment, could actually prove detrimental in some way?

Okay, I know that now a bunch of you are thinking, "This guy IS nuts. Letting detritus accumulate in an aquarium is bad news. A recipe for problems- or worse. And not only that, he has no idea of the implications of what he's suggesting."

Well, as far as the first part of your thought- Yeah, I could be a bit "crazy." On the other hand, I think I do have some idea of the implications of what I'm postulating here. First off, remember, I'm not suggesting that everyone throw away their siphons and just allow shit (literally!) to accumulate in their aquarium substrate in the interest of creating a "food web."  

No sir.

What I am curious about is if there is some benefit in a botanical, blackwater system, of encouraging a bit more fungal and microbial growth, utilizing, among other things, the organic detritus that inevitably is produced in a well-managed. well-populated aquarium.  I mean, if you're doing water changes and removing uneaten food, dead fishes, aquatic plant leaves, etc., you're already significantly reducing the "food inputs" available to the organisms on the low end of the food chain, right?

In a typical aquarium, well-maintained with regular water changes and removal of detritus, our fishes are almost 100% dependent upon us to provide food, right? So, why not promote some of this detritus to accumulate- as part of the "supplemental food" for your fishes. I've done this several times now with great success, and no longer see it as some bold experiment or stupid stunt. 

I think it's a valid practice if understood and executed upon correctly.

Once again, we're questioning our age-old practices not to be a pain in the ass...rather, to see if what we're doing IS truly the best practice, and to see if there might be a better way. A more natural way. One which ties in with the way we manage our aquariums as a whole- botanical-style or otherwise. All of these things are potentially interrelated, and all of them are worth taking a look at with a fresh perspective. 

The big winners here: The fishes, the hobby, the hobbyist..and of course, the natural habitats-because if we understand how fishes and their habitats are intertwined and related, we will have a better understanding of the need to protect and preserve these priceless ecosystems for future generations to enjoy.

As usual, today's

rambling discussion likely leads to more questions than answers. However, some of these questions- which address some of the most fundamental, long-held beliefs and practices in aquarium-keeping, might help us make not only more "mental shifts", but true breakthroughs as we rediscovery the utility of the elegant, yet "complex simplicity" that nature has engineered over the eons.

Embracing- not fighting- nature in a more complete sense just might be "the next big breakthrough" in aquarium keeping. 

And it all starts with thinking about the environments of our fishes, and how to replicate them in the most comprehensive, realistic, and functional way possible.

We've got this.

Stay excited. Stay observant. Stay curious. Stay dedicated. Stay creative. Stay diligent...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

July 31, 2020


The value of ideas.


Time for some new aquariums in my home....Always a cool thing, but it's also a sort of challenging thing, right?

And it always starts with...ideas.

I mean, I have a bunch of ideas that have been percolating in my head for...well- years! Like many of you, I keep a little notebook full of sketches, thoughts- little ideas for new tanks. I've been keeping it forever, and it's helped me realize some pretty amazing projects over the years! In fact, the idea for Tannin came from that little notebook!

All of these ideas...

And yet, I still have that same feeling of... Perhaps, restriction? Frustration? Not sure what it is- when you just have to have one tank to make it happen...Ridiculous that I should feel this way- I mean, I'm incredibly fortunate to be able to build a few tanks. Of course, in my head, the "disconnect" is that I have unlimited ideas...many of which, for a variety of reasons, never really get out of the "theoretical" phase!

I used to laugh at news reports when NASA would announce that it committed $4,000,000 to the study of building a starship, or some other thing for which the actual capability doesn't even exist yet- and likely won't for decades, if not longer. I mean, why? And yet, I kind of understand it now...It's like, I am appropriating all of this "mental capital" to study some of my concept tank ideas that perhaps I really don't have the means to pull off- just yet.

Well, that's kind of fun, actually! What hobbyist doesn't look at their tank and think (or even say!), "Next, I'm gonna build a tank that has___________."  

I think that's what keeps us moving forward, right? Big ideas...Ones that we do execute on, though.

So anyways, I've narrowed down my range to a few concepts- each one quite different from the other.

I go back and forth, getting mentally committed to one idea, and then seeing a really great piece of driftwood or something which takes me into a different place...Or I see a video or image of a wild habitat that gets me going, and then I get turned around into one of the many other ideas I've been playing with...

Wow. Crazy.

I get really distracted easily, when it comes to aquarium stuff!

The goal is not to get into a loop of "analysis paralysis" and never make a move simply because I'm "still planning..." Yeah. I've seen guys do that and the tank sits empty and collects dust cobwebs while they are "contemplating."


You see, like many of you, my imagination, appetite, and enthusiasm are often larger than my ability, time, or means to get the job done. I've concluded that to do all of my crazy concept tanks, I'd probably need like 17 aquariums of all shapes and sizes, many with technologies and components that would carry a breathtaking price tag- if they exist at all... 

And, this is AFTER I've eliminated some of the early front runners, like the intertidal  Pipefish Mangrove tank, the Amazonian waterfall tank, the monospecific Acropora microcaldos tank, the "Nothobranchius Temporal Pool" concept tank (ask me about the "mud hole" idea I've been playing with sometime), and others that are earmarked for some "indefinite future date...."

So, I kind of have this personal thought about "ideas."

They're worthless.


Okay, that sounded a bit harsh. Let me clarify a bt.

I mean, if you're not going to do anything with them, they're sort of just "nice things" to have- maybe inspiring-but you need to act on them or they are just...theoretical, right? 


I don't keep "theoretical" tanks. 

And, I realize that there are limitations that we all have- Space, time, money, etc.- and that these temper many of ideas from being executed. I suppose that is part of the reason why I've changed my thinking about so-called "nano"-sized tanks over the past few years. Because their smaller size and ease of use helps you rapidly iterate from idea to completed system quickly and easily! I've had a lot of fun with them lately.

One of the best things about my business is getting to help fuel the dreams of other hobbyists. It gives me great pleasure to see you guys enjoying the hobby, and motivates me to do more.

And of course, when it comes time to do my own tank, I have to weed through all of these crazy ideas- some of which challenge me in ways I hadn't even considered. Some are just fun to play with.

Others launch me and Tannin into entirely new directions- those are the best ideas!

Okay, so maybe not ALL ideas are worthless.

I'm curious about what your "next" tank is going to be, how you arrived at the concept, and if you actually have gotten out of the planning phase..

So many of us are pushing the boundaries in aquarium technique by utilizing elements of blackwater, botanical-style aquariums, and many more techniques to discover, develop, and refine. With so much interest in our "dark world", we're seeing an exciting influx of new people, new energy, and new ideas- all of which will enrich and enhance the art and science of aquarium keeping, for the benefit of everyone who participates in this awesome hobby!

I took the time to write down and share everything I learned with my fellow hobbyists. Shared everything that I've learned and thought about- still do- in this blog and elsewhere. I'd like to see more of you doing that, too!

I'm not that unique.

I am just an average guy with an above average interest in a rather arcane subject within the aquarium hobby, and I pushed to learn as much as I can about it. Lots of you do the same...have for decades.

And whenever I tried new ideas, I would encounter some pushback from those who felt that they couldn't be pulled off. So-called "constructive criticisms" delivered in a most unconstructive way.

Many of you were dabbling with unusual ideas of your own, and we've traded "war stories", shared ideas, discuss our successes- and failures. We collaborated.

It worked beautifully with the evolution of the botanical-style aquarium approach: We took an idea which was typically dismissed, or seen as some sort of "side show" and looked at it more seriously, more procedurally...With an emphasis on observing Nature and attempting to understand and replicate some of its aspects in our tanks.

And we are seeing the emergence of blackwater, botanical-style aquariums as a legitimate methodology to successfully keep and breed a wide variety of fishes. We learn new stuff every day- together. So, yeah, I suppose that's another example of the value of ideas!

This is the way you push out into the unknown and weather the unwarranted "criticisms" or plain old attacks. You DO your thing. You focus. You find others who have similar interests and share ideas. You collaborate. And most of all, you share. Without fear of judgement. And without expectation of anything, other than perhaps inspiring others to follow the path you've taken if they desire, and to expand on your idea and improve upon it.

It's hard to take criticism. I know. 

Especially when it's for something you hold near and dear, and work with daily. However, in the aquarium world, like in so many other places- it comes with the territory.

However, it's harder to allow one of your ideas to shrivel up and die without ever being executed because you were afraid of criticism.

For those of you taking on your new ideas, and pushing out into new territories- new frontiers:

Move forward. Bravely. 

Take comfort in the fact that you are trying. Take comfort in the fact that your work may inspire others...and in it's own little way, perhaps change the aquarium hobby.

You're not foolish.

And your ideas aren't, either.

As long as you execute on them.

Whatever idea you decide on for your next aquarium- just DO SOMETHING!  Dream about it. Create it. Study it.

Stay bold. Stay creative. Stay thoughtful. Stay diligent...

And Stay Wet.


Scott Fellman

Tannin Aquatics

July 30, 2020


The dynamics of botanical-style aquariums

 Botanical-style aquariums are a bit different. Yet, they're not THAT different from aquarium systems we've become more accustomed to over the years, right?


Our botanical-style aquariums are not "set-and-forget" systems, and require consistent basic maintenance (water exchanges, regular water testing, filter media replacement/cleaning), like any other aquarium.

They're truly dynamic.

We have developed some regular practices in the botanical-style aquarium hobby.  Perhaps one of the most "time-honored" practices is the idea of replacing decomposing materials with new ones regularly. This is one unique "requirement" as part of their ongoing maintenance which differs botanical-style aquariums from other types of aquariums.

It's a regular thing; almost a revered, ritualistic sort of thing among us hardcore botanical-style aquarium freaks.

The "topping off" of botanicals in your tank accomplishes a number of things: first, it creates a certain degree of environmental continuity- keeping things consistent from a "botanical capacity" standpoint. Over time, you have the opportunity to establish a "baseline" of water parameters, knowing how many of what to add to keep things more-or-less consistent, which could make the regular "topping off" of botanicals a bit more of a "science" in addition to an "art."

In addition, it keeps a consistent aesthetic "vibe" in your aquarium. Consistent, in that you can keep the sort of "look" you have, while making subtle- or even less-than-subtle "enhancements" as desired. 

Yeah, dynamic.

Because not only does Nature evolve our tanks by decomposing botanical materials over time, but we as hobbyists take part in this process by replenishing them with fresh materials.

Botanicals should be viewed as "consumables" in our hobby- much like activated carbon, filter pads, etc.- they simply don't last indefinitely.

And, of course, "topping off" botanicals helps keeps you more intimately "in touch" with your aquarium, much in the same way a planted tank enthusiast would by trimming plants, or a reefer while making frags. The side benefits are immediately apparent, too: When you're actively involved in the "operation" of your aquarium, you simply notice more. You can also learn more; appreciate the subtle, yet obvious changes which arise on an almost daily basis in our botanical-style aquariums.

Over the years, I've found that one of the things I enjoy doing most with my blackwater, botanical-style aquariums (besides just observing them, of course) is to "top off" the botanical supply from time to time. I feel that it not only gives me a sense of "actively participating" in the aquarium- it provides a sense that you're doing something that Nature has done for eons; something very "primal" and essential. Even the preparation process is engaging.

When you think about the materials which accumulate in natural aquatic habitats, and how they actually end up in them, it makes you think about this in a very different context. A more "holistic" context that can make your experience that much more rewarding.

Nature does it's own version of this "topping-off" process, too, of course!

Many bodies of water which meander through jungles and rain forests are constantly being "restocked" with leaves, seed pods, branches, and other botanical materials from the surrounding vegetation- some of which are knocked into the water by weather, wind, animal activity, etc. Depending upon the velocity of the water, its depth, etc., they may aggregate right where they fall, or be gradually re-distributed downstream by the current.

Interestingly, in places like the rain forest streams of Amazonia, biologists have observed floating leaf litter beds which hold together for quite a long time- almost becoming known "features" in the aquatic "topography" of the flooded forests (igarape) and streams of the region!

I have an obsession for small little tropical streams; their evolution, form, and function.They are remarkable little habitats, with literally thousands of different fishes found residing in them. 

The definition of a "stream" is: "...a body of water flowing in a channel or watercourse, as a river, rivulet, or brook..."

And of course, these little bodies of water flow through jungled areas, where they're bound to pick up some leaves, twigs, and other plant parts as they wind along their path. Leaves, the "jumping off point" of our botanical obsession, form a very important part of these stream habitats.

It is known by science that the leaf litter and the community of aquatic animals that it hosts is, according to one study, "... of great importance in assimilating energy from forest primary production into the blackwater aquatic system." 

There is something that calls to me- beckons me- to explore, to take note of its intricate details- and to replicate some of its features in an aquarium- sometimes literally, or sometimes, simply taking components that I find compelling and utilizing them in my tanks.

Streams also function as a means to preserve the nutrients that would be lost to the forests which would inevitably occur if all the material which fell into the streams was simply washed downstream. The fishes, crustaceans, and insects that live in the leaf litter and feed on the fungi, detritus, and decomposing leaves themselves are very important to the overall habitat.

In this world of decomposing leaves, submerged logs, twigs, and seed pods, there is a surprising diversity of life forms which call this milieu home. And each one of these organisms has managed to eke out an existence and thrive. 

A lot of hobbyists not familiar with our aesthetic tastes will ask what the fascination is with throwing palm fronds and seed pods into our tanks, and I tell them that it's a direct inspiration from nature! Sure, the look is quite different than what has been proffered as "natural" in recent years- but I'd guarantee that, if you donned a snorkel and waded into one of these habitats, you'd understand exactly what we are trying to represent in our aquariums in seconds!

Of course, water chemistry of flooded forests and streams is influenced by the many terrestrial components of the habitat. The trees in the ecosystem enrich the habitat and the resulting organic detritus from decomposing bark and organic exudates from the trees themselves help concentrate nutrients within the ecosystem itself.

Learning more about the dynamics of stream habitats and the ecology of the surrounding terrestrial environments is just one fascinating and compelling area of study that we as aquarists can really get into.

Yes, it requires some study. It requires trying some new and seemingly wacky ideas (encouraging the accumulation of detritus, decomposing leaves, and epiphytic biofilm growth, for one thing!), and embracing some different aesthetics in our aquariums.

Let's focus on this "functional" dynamic for a second. When we look to Nature, it's increasingly obvious that we can replicate much of it in our aquariums.This quote from a paper by Mendonca, et al, tells me so many cool things about the habitats we love to replicate:

"In Central Amazonia, terra firme environments (uplands that are not seasonally flooded) are drained by streams that have acidic waters due to the presence of humic and fulvic acids. The waters are poor in nutrients and the forest canopy impairs light penetration to the stream surface, so aquatic plants are virtually nonexistent (Junk and Furch, 1985; Walker, 1995). In these oligotrophic environments, food chains are dependent on allochthonous material from the forest, such as pollen, flowers, fruits, leaves, and arthropods (Goulding, 1980; Goulding et al., 1988; Walker, 1991). However, small fishes are frequently abundant, and 20 to 50 species may occur in a single stream (Lowe-McConnell, 1999; Sabino, 1999)."

In streams, studies indicate that an increase in species "richness" is positively related to the habitat complexity and shelter availability as well as current velocity and stream size, and that substrate, depth and current speed are among the most important physical features in many bodies of water, which contribute to the formation of numerous "microhabitats", all with fascinating ecology, environmental parameters, and fish population diversity.

 Stuff we've barely tapped into in the aquarium world yet!

The implications of this information for aquarists are profound and fascinating, and understanding, interpreting, and applying some of these numbers and concepts can potentially lead to some fascinating breakthroughs in aquarium work.

However, we have to "get out of our own way", first.

We're talking about taking the lead from Nature- looking at it as it IS- and about using this stuff to create aesthetically compelling, dynamic, and physically functional aquariums. There is always the danger of going too far, and falling into that cliche of closed-minded superficial replication that is, in my opinion, consuming the aquascaping and biotope aquarium world, so use the information you find with a bit of interpretation...but make use of it nonetheless.

It's time to create awesome-looking aquariums that also function like the natural habitat which they intend to replicate.


They may not be "pretty" in the conventional aquarium sense. 

They might not look or function like a "traditional aquarium", and they might not be attractive to many in the same way a more "high concept" planted tank is...And that's okay. It's important to understand that we're going in a different, very unique direction- one which has a different goal, and will, with a different operational approach- yield a very different outcome.

All of these things are very interesting, and so much is yet to be learned and experienced by us as hobbyists in relation to leaf litter and botanicals in our aquariums. Yet, one can only hope that many of the positives which occur in natural habitats comprised of leaf litter and botanical cover will occur in our thoughtfully-managed aquariums.

The day will come when we have a better understanding of what's really going on in leaf litter beds in our tanks, and that these materials won't be coveted just for their ability to impart tannins and humic substances, or for creating a different aesthetic, or for lowering pH and tinting the water, but for the true biological "richness", diversity, and utility they provide.

I celebrate our effort to understand, execute, and embrace the dynamic processes which occur within them, and allowing all of the life forms which reside within them to benefit from them.

Stay engaged. Stay bold. Stay diligent. Stay patient. Stay studious...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


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