As we get more and more into this botanical-style, blackwater thing, we learn more and more interesting things about how these types of aquariums perform over the long term, and how you manage the systems with all of the "stuff" in there, breaking down and imparting their tannins, humic substances, and bound-up organic materials.
From a physical standpoint, we don't really have a problem with the leaves, seed pods, and other materials breaking down in the aquarium. Once you've made that "mental leap" to accept this as a very natural look and function, then it's a matter of making it all work. Fortunately, we as a community have moved beyond the initial perception (particularly from the "nun-initiated") that, just because our water is brown, and because our tanks contain decomposing leaves, that they're "dirty" or "out of control", or "poorly maintained." (all things we heard a lot a couple of years ago...and still do on occasion)
Now, although we've addressed this stuff before, with so many people getting into the game, it makes sense to review it from time to time- especially in light of the many different types of setups that our community is utilizing botanicals in (i.e.; planted aquariums, hardscapes, fry rearing tanks, dedicated botanical/leaf litter systems, etc.). And let's face it, with more people, comes more knowledge, more refinement of technique, and more opportunity for us all to learn together!
One of the concerns we hear a lot is that when botanicals (specifically, leaves, but everything else, too!) break down, they end up in little pieces that can end up creating a bit of a mess if they start accumulating in filter intakes and such. It's a valid question, because, let's face it- we've been "trained" throughout our fishy careers to look at debris and such with a certain degree of disdain- not only from an aesthetic standpoint- but from a maintenance one as well!
First off, as we all know, stuff does break down over time. Some leaves, like Catappa, tend to be less durable than others and are far more "transitory" in nature than say, Guava, Magnolia, or Jackfruit, which tend to be more durable and take a much, much longer time to fully break down in the aquarium. That being said, Catappa tends to break down gradually, over a period of a few (maybe 2-3 weeks, depending on various factors, such as temperature, pH, water movement, fish foraging, etc.), and you'll see it breaking up, at which time you can either physically remove it, or leave it in to completely break down.
Now, with regard to the decomposing leaves getting sucked into filters and such...it can happen, but I have not personally had this be a factor in my tanks. And coming as I do fro ma reefing background, where we are incredibly paranoid about debris that can clog overflow weirs and intakes and such, I am acutely aware of the need to monitor this stuff. However, I have personally found that, unless you're directing a lot of flow right into the botanical bed (which you wouldn't likely do, because you'll have stuff being dispersed everywhere-you're more likely to use indirect flow), most of the debris that occurs from leaf/botnanical breakdown tends to stay "low" in the tank, where it is easily removed manually if desired. Surface skimmers, or intakes placed higher up the water column are one easy solution, but a combination of stuff usually does the trick.
And, believe it or not, I've found that one of your best allies in keeping stuff out of the water column (and therefore, filter intakes and such) is...biofilm! Yes, biofilm, the previously vilified, snotty-looking stuff that accumulates on your botanicals over time, causing much consternation for the uninitiated or neophyte "tinter", until he/she realizes that they are ubiquitous in nature, and highly beneficial as a food source and localized nutrient processing "vehicle." This stuff actually helps function as a sort of "biological glue" which not only weighs down some of the leaves and such, but holds them in place, keeping them from floating all over the place should they catch a favorable current.
And while we're at it, a quick refresher on biofilms: They are essential and absolutely natural. When terrestrial materials fall into the water, opportunistic life forms, ranging from algae to fungi to bacteria, will colonize the available space, taking out a living as they compete for resources.
In addition to helping to break down some of these terrestrial materials, the life forms that inhabit submerged tree branches and such reproduce rapidly, providing forage for insects and aquatic crustaceans, which, in turn are preyed upon by fishes. Yeah, a food chain...started by a piece of tree or plant that fell in the forested was covered by water during periods of inundation. Amazing.
And sure, the aesthetic "shift" that we make when we accept the presence of biofilms, decomposition, and even a bit of algae is hard for many of us.
I get it. We, as a group, like things orderly. We like to see things looking "pristine" and well-kept...and I understand that well. For decades I was the guy in who's tanks you wouldn't see a speck of algae...Like, none. My reef tanks were so clean-looking that one of my friends jokingly suggested that "you could give birth in there..."
But guess what? "sterile" is not natural. At least, not in most aquatic habitats. I see how planted tank people take great care to optimize the environment for the plants, eliminating any algae they can find, in favor of lush plant growth. And that makes sense in that context. However, when I see systems comprised of perfectly "ratio-obeying" rocks, covered in mosses, with neat "lawns" of low-cut, perfectly manicured grass on the substrate, the word "natural" doesn't immediately come to mind. Rather, I find them stunningly beautiful; artistic- much in the same manner as a finely-kept garden or planter box. Respect for the enormous effort and talent that went in to planning, executing, and maintaining the tank. However, I take exception with the (IMHO) overstated and all-encompassing moniker of "natural-looking" ascribed to many such tanks. Natural, perhaps in the sense that plants are growing there, with fertilizers, etc...but that's about it, IMHO.
So, understanding that, while biofilms and decomposition are part of the biological "load" of the aquarium, they are not inherently "bad" or "dangerous"- they're part of the natural ecology of underwater systems, and it's good to see hobbyists finally embracing them and their cohorts in our aquariums!
In fact, most aquatic animals simply thrive in their presence...We've just never "embraced them" before...rather, we've removed 'em immediately, much the way one might squash an ant, or pull a weed from the garden...not moving beyond the initial revulsion, and failing to take into account the true "functionality" they bring to an aquarium. We've talked about biofilms in detail before, and I think it's not bad to give ourselves a "refresher" on them now and then!
Now, all of our "zen-like" acceptance of the wabi-sabi nature of leaves and the presence of biofilms and detritus and such, but the fact is, when you add materials like leaves and botanicals into your tanks, they are part of the biological load that your system needs to adjust to. We've talked about it a lot before, but there are dangers of adding too much too fast. The beneficial bacteria which break down biological waste can only grow so fast, so a huge influx of leaves or botanicals in a brief time span in an existing aquarium can certainly have some negative effects, including a rapid decrease in oxygen levels. The key, as we've stressed repeatedly, is to move slowly, incrementally. Sure, one you gain experience, you'll know how far you can "push it", but nature doesn't really care about your "experience"- if the conditions aren't right and the bacteria in your system cannot accommodate a rapid significant increase in bioload, she'll kick your ass like a personal trainer!
Respect nature. Learn from her.
We benefit immensely when we consider our botanical-style aquariums- or any type of aquarium, for that matter- as a small ecosystem, which has inputs, outputs, cycles, and rhythms, all of which are dictated by the fungi and bacteria which are the real "workers" in our aquariums. We can assist by performing the same types of maintenance we'd do on any aquarium: Regular water changes, filter media cleaning/replacement, and common sense stocking and feeding of our fishes. Much like a reef tank, or a planted aquarium, for that matter, I believe that a botanical-style aquarium will find a sort of "functional equilibrium" over time which works. It may take a bit of playing with stocking, botanical additions, and husbandry practices by you to help your system "find" it's path- but it will happen. And make no doubt- a botanical system will "correct" for any errors via chemical imbalances, CO2 increases, and overall functional challenges if you push.
Active management is part of the game with botanical-style aquariums. Although they settle down nicely once established, they are simply not "set and forget" aquariums (as if ANY of them really are, if we're honest with ourselves?)...
This is not new.
Conceptually, it's not unknown to us as aquarium hobbyists. However, the context in which this occurs- and accepting things like decomposition, biofilms, leaves on the bottom, etc., as part of the visual "ecosystem" - is a bit different. They're more "overtly functional"- that is, you can actually "see" the tangible evidence of the processes in many cases, which would otherwise be occurring out of sight in other systems (in the filter, under the sand, in "cryptic areas" in the tank, etc.). Not everyone will like this. Not everyone will agree with the philosophy or concept as I'm presenting it here. It's a point of view that accepts way more than we're used to- and also one in which we 'cede" a bit more control to nature, and question more...and have much, much more to learn about, too.
That makes some hobbyists uncomfortable, and that's perfectly understandable. There is still a lot of room for experimentation and input from hobbyists at all levels.
As a botanical/blackwater aquarium enthusiast, you're going to become more attuned to these processes. Much will come out of necessity, and other parts of the equation will perk your fascination, spurring you to research more. You'll want to educate yourself more on the nitrogen cycle, the role that terrestrial materials play in the aquatic environment, and how fishes and other aquatic organisms "fit" into the grand scheme of things. You'll become as much an "aquarium ecologist" as a fish keeper!
It's an always-changing, continuously-evolving cycle of life. And we get to see it all in the comfort of our own home.
I don't think we as aquarists couldn't ask for much more than that.
Stay bold. Stay observant. Stay involved.
And Stay Wet.