Questions and answers on our new brackish-water tank...The beginning...

As we've finally started working with our brackish water aquarium in the office, we've received a large number of questions on various topics associated with the aquarium.

And why not answer some of 'em right here?

Obviously, this is not a "ground-breaking" tank, and it's in its infancy, but I think it is a system that embraces our love of the whole "botanical-style" brackish tank; something we hope to see more of in the hobby! The amount of interest we've seen in it is really exciting, and encourages us to press forward with some more cool ideas for this system!


Is this tank modeled after a specific location, or just the mangrove habitat?

Great question, actually! We decided at the outset that weren't going full-on biotope aquarium, with every fish, shell, leaf, etc. coming from a specific geographic location. Rather, we wanted to replicate a "generic" brackish-water mangrove habitat, with a dark bottom, lots of mangrove roots, some leaf litter, and live mangrove propagules accenting it.

There is something really cool to me about simply sharing our idea of the "tinted" botanical-style brackish tank in operation first, and then we (and others!) could go down the biotope route down the line.



What size is this aquarium? How is it filtered?

This is an "all-in-one" style aquarium from Innovative Marine; their Fusion Mini 40, which is 40 US gallons, and has dimensions of 24x20x19 inches. The aquarium features a built-in overflow weir and multi-chamber filtration behind the tank. Other than some filter pads and a few small ratchets of activated carbon, I utilize the rear compartment more as a "sump", providing primarily biological filtration, space for a heater, pump, auto top-off, etc, as well as providing a space for settling of detritus and additional water volume. You could pack in stuff like boils, chemical filtration media, etc. if you want. The pump is a Sicce "Syncra Silent 1.5", pushing 357 GPH. we use an EcoTech Marine "Vortech" MP10 on "Lagoon Random Mode" for additional flow within the system.



What specific gravity and other parameters are you maintaining? How do you keep the specific gravity consistent?

We target a specific gravity of 1.004, and I use Instant Ocean mix to achieve this. Water temperature is 77.5 F /25.2C. The pH of the water is 7.6, and the alkalinity (KH) is 7.  

An interesting set of readings...

Oh, by the way, my fave testing equipment for specific gravity is a digital eliminates any "interpretation" and guesswork when you're trying to determine the low specific gravity that we play with!

We maintain the specific gravity consistent by use of a very simple automated top-off system, the "Smart ATO Micro", which consists of an optical sensor, which you place in your tank at the depth you want the water level to remain at. When the system detects that the water level has dropped, it activates a tiny but incredibly powerful DC pump, which you place in a reservoir or other container below the tank, filled with fresh water.

I had a custom acrylic reservoir made by my reefing pal/celeb, Marc Levenson, who's website, is an ultimate source for the DIY reefer. And unlike some other (inexplicably) much-loved and well-known "DIY" hobby people, Marc is actually a really nice guy and will take the time to work with you!

Check his site out! 

The pump injects enough water to bring the water level back to the predetermined depth. ridiculously easy and incredibly accurate! I use this system in all of my open-top aquariums, which are subject to evaporation. It's an easy way to maintain consistent water parameters in brackish (and blackwater) aquariums, which require consistent parameters for optimal health of their inhabitants.



What is the wood in that tank?

It's a combination of our Mangrove Root Sections and Mangrove Branches. They're PERFECT for the look we're trying to achieve, and super-easy to use in a "vertical" format. One thing about mangrove wood, however- it's kind of a "dirty" wood (particularly the root sections", and will accumulate algae an biofilm rapidly and significantly (which BTW, is entirely consistent with the habitat we're replicating!), and you need to be patient/accepting/diligent (or all of the above) to deal with it. It will ultimately become more-or-less "pristine" over time, but you need to wait..or employ some snails, like Nerites, etc.


Are those live oysters on the mangrove branches?

No, actually. They are Oyster Shell Halves, which we patiently glued to the branches with glue. We like the viscosity/"stickiness" of EcoTech Marine Coral Glue, a fave from my reefing work- but you can use any cyanoacrylate kind of glue and a little patience. Gluing multiple shell halves together on the roots takes time, but the effect is pretty cool, IMHO...I was inspired by the pic below.

I achieved exactly the effect I was looking for...If I were to do it over again, I think I might actually have used more, extending them a bit deeper below the water line. Regardless, I'm really stoked with how this turned out!


Are you incorporating live mangroves into this system?

Yes. We are utilizing some mangrove propagules that we've been sprouting in our "window garden" over the past several months in brackish water (it's important to sprout your mangroves in the same water considitons ( i.e.; specific gravity) in which they will ultimately be residing.) 

We've secured the sprouted propagules to the mangrove root sections within the tank, with the ultimate goal for them to "touch down" with their prop roots into the substrate. This is a long-term process, as the mangrove is not the fastest-growing plant out there. However, we play a "long game" and are very patient to let them do their thing and gradually let the roots work their way down into the substrate and for the branches and roots to sprout above the waterline in their own time...


What kind of substrate are you using? What are you growing?

This is one of the fun parts for me...And perhaps even a bit "controversial", in that I'm using a very "rich" substrate in a tank that I'm not really growing aquatic plants in. My rationale for utilizing such a substrate was to attempt to recreate the environment and to a lesser extent- the function, of a rich, biologically-active substrate.

I'm using a mix of a few different materials- Eco System "Miracle Mud", CaribSea "Refugium Mineral Mud", very find aragonite sand, organic compost, and some fien, brownish gravel to give the whole thing a sort of "muddy" look. 

And ultimately, when the live mangrove propagules I've sprouted in my tank "touch down" in this milieu, they'll have a very "fertile footing" to grow in! Now, in the mean time, I am seeing a bunch of small life forms (likely "hitchhikers" from my mangrove propagules) start to emerge from the substrate...very cool. And of course, with other materials (like fish waste, organic detritus, and decomposing leaves) adding to the "mix", it's only going to get better! I was originally thinking of using the adaptable Cryptocoryne ciliata as a plant in the substrate, but after seeing the look of the tank once it was filled, I felt it would simply be "too much" in the 'scape that I've developed...Maybe down the line.


Are you using leaf litter in there?

We're using a combination of Red Mangrove Leaves and Malaysian Yellow Mangrove Leaves in a combination. I'm gradually building up the amount of leaves, while not going too crazy with them. to keep a sort of open look. I'll be replenishing them as they decompose. They are helping to enrich the substrate, while providing a cool aesthetic as well.

Obviously, there is a lot more to this tank to talk about...and we'll cover your additional questions (like, how we're lighting the damn thing and oh, yeah, what FISHES we're putting in there!) in the next installment of this look! The word of Estuary is just getting started, and we're all learning some cool stuff together, just like we did in the blackwater world!

In the mean time, I hope that this admittedly brief look has at least answered a few of your questions and maybe inspired you to play with this stuff! Feel free to hit me up on social media, email, or in this blog if you have more questions! 

Stay curious. Stay engaged. Stay creative. Stay excited...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


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