The evolved brackish tank....The end of a journey- the beginning of a voyage.

As we discussed yesterday, there is that strange dichotomy of my love for the long-term and the need to share new stuff with the world. And that involves changing up some stuff; moving on to newer things. 

Aquariums, like everything we do here, are a combination of personal passion and the desire to share new ideas. And that involves letting go. It's time to wrap up our brackish-water mangrove aquarium (V 1.0) to move on to something that we hope will be equally as exciting and inspiring for our community.

Now, the brackish tank is cranking- itcould have gone on indefinitely. Indeed, it will, in that the mangroves will be used in a different display and the fishes relocated to a new tank as well. This aquarium- over 2 years in the making- served its purpose and fulfilled its mission beyond even what we had initially expected!

The idea, of course, was to demonstrate how we could bring some new life and a slightly more realistic approach to the rather staid, traditional brackish water aquarium as the hobby knows it. Of course, our "slightly more realistic approach" is actually somewhat of a radical departure from the usual brackish water tanks which have dominated this obscure niche for decades.

As a decades-long reef aquarist and blackwater, botanical-style aquarist, how could I resist a "fusion" of the two? Besides, it was another example of the world being the way it really is, and how we as hobbyists chose to interpret it in our aquairums. And I personally felt/feel that we've been sort of choosing the safe, "established", generally unrealistic, and altogether boring path in brackish for decades! 

So I had this idea to portray the brackish environment as it really is...not some sanitized, aquarium aesthetic version. And of course, as you know, if an idea is a bit out of the norm, we're all over it. It was time to "evolve" brackish aquariums.

And when an idea like an evolved brackish system pops into our heads, it's time to give it a whirl, as they say.

And it starts with a few important pieces of hardware; some stable environmental parameters, and patience...

Let's talk about the operating parameters of this tank for just a second.

We initially targeted a specific gravity of 1.004; however, for a variety of reasons, over the lifetime of the aquarium, we migrated it up to 1.010. I use Instant Ocean salt 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...And we can talk more about this stuff in a future installment of "The Tint", as it's pretty interesting! 

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 lower specific gravity levels that we play with! If you're going to play in this "slightly salty" world, a digital refractometer is a great investment!

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.


There are several physical materials that are the basis for our concept of the "evolved" brackish-water aquarium:

-Mangrove branches

-Rich substrate

-Mangrove propagules

-Mangrove leaf litter

-Tinted Water

Let's start with the Mangrove wood/branches.

Mangrove is a surprisingly "dirty" wood; in other words, there is a lot of "stuff" in and on its surface tissues. Makes sense, as it grows in pretty "biologically active" habitats. It fosters a lot of biofilm and other growth when submerged, so you definitely want to take the time to soak it like any other driftwood before use, and to scrub the exterior surfaces of biocover from time to time during the preparation process.

We work with two types of wood: 

Mangrove branches- These are the actual branches of the mangrove tree, trimmed and stripped of any leaves. Interestingly, if you invert them, you're looking at what is essentially the same "configuration" as the aerial roots the tree sends out, and this is a remarkable, natural representation of the the root for our purposes! Thin, gnarly, and intricate, these pieces are super easy to work with in the aquarium, and will help you create the "backbone" of what we think is the most authentic-looking mangrove biotope aquarium possible! 

Some of them are truly large, which will create a dramatic effect in medium to large aquariums. Depending upon the size of your aquarium, the look you're trying to achieve, and the size of the branch(es) you purchase, you could use a few pieces, or just "one and done!" They are lightweight, and you might need to get clever in securing them into the substrate by weighting them with shells, buttressing them with sand/rock, or even using plant weights.

Mangrove root sections- Just what they sound like- these are thick, woody sections of the prop root of the mangrove tree, and they are cut into little "log-like" sections, varying in both size and thickness. However, they are much, much thicker and more "substantial" in general.   

Now, like any wood, there will be some leaching of tannins (although it's less pronounced with the branches than with the root sections, in our experience) and the growth of some biofilms. This is remarkably durable wood, and lasts a very long time. The branches are extraordinarily flexible, too! 

Far be it from us to tell you just how to use these pieces in your aquarium, but I'd really be remiss if I didn't give you just a bit of advice, right? 

First off, as mentioned above, I'd use the branches in an "inverted" orientation, with the multiple "branchlets" becoming the prop roots of our simulated mangrove habitat. I'd intermingle the branch(es) into a few of the thicker root sections, to give a sense of depth, scale, and structure. To any of these sections, I'd break out the super glue and secure various types of shells to the surfaces. On the submerged sections, you can secure the tiny shells of the Littorina sp. (Mangrove Periwinkle), which look really cool on the roots! 

On the top, above the "water line", I'd incorporate the halves of our small oyster shells, to simulate the habitat of the Mangrove Oyster, Crassostrea gasar. This will create a very unique look in your brackish-water aquarium. 

The interface of the water/roots/substrate is a fascinating ecological niche with tons of aesthetic and functional possibilities. It's dynamic, ever-changing, and offers the opportunity to create a really unique-looking aquarium! 

Substrate is a huge and perhaps overlooked component of the brackish water aquarium- and the wild habitats as well.

We've utilized a very rich mix of aquatic soils, similar to what has been used in "dirted" tanks by aquatic plant geeks, yet with a buffering component (finer, aragonite or calcareous substrates) and commercially-available marine biosediment materials.  We created a "workable" environment to grow mangroves with such a substrate.  And by managing the water quality with regular, frequent water changes, and careful, automated topoff to keep specific gravity constant at a brackish level (like-this is a fundamental thing), I believe that we have been able to simulate this environment on at least a superficially functional level.

Kind of like what we're doing with blackwater, leaf-litter-bed aquariums?

Um, yeah...totally.

Now, we have to learn a bit more about the impact of high-nutrient substrates, decomposing leaf litter and such in brackish systems, but it's a totally cool experiment, IMHO!

Mangrove habitats also function as fish "nurseries" and feeding zones, assist in preventing shoreline erosion because of their ability to trap sediments in the low-energy waters of brackish estuaries and breaks up wave action within their maze of prop roots. These prop root systems are just screaming at us as fish geeks to play with. I've waded, snorkeled and scuba dived in Mangrove systems many times, and am always blown away by the myriad of tempting aquarium possibilities that they inspire!


Numerous "sublittoral/littoral" organisms utilize the prop root zone of red mangroves as their primary habitat. The "prop root zone" provides sessile filter feeding organisms, like  such barnacles, muscles, tunicates, and bryozoans with a perfect environment in which to live and reproduce.  There are sponges in brackish ecosystems, but they are highly specialized feeders, often deriving sustenance from a very specific type of dissolved organic food source, so we're unlikely to be working with them. Oh, you also have the "seldom-kept-in-aquaria-intentionally" polychaete worms and "boring" crustaceans, like isopods.

Yeah...there is so much going on in this much for us to play with as hobbyists, In fact, part of me is actually a bit guilty for unleashing the "Estuary" idea so early on (we were in operation around 2.5 years when we did) in Tannin's existence, as we're just now starting to really venture out and unlock some secrets in the blackwater/botanical game...But I think that the two can develop together and spur on new hobby advances.

In fact, I think that they already have...

And of course, there are the Mangrove propagules.

I've sprouted them in a bright windowsill, and then transplanted them to the aquarium when they start developing some nice roots and leaves. There are some tricks to this, which we'll touch on in a later piece!

One key concept when it comes to using mangroves in your aquarium: Sprout the propagules in the same water conditions (ie; freshwater, brackish, or marine) that you intend to keep them in for the duration. Notice that , in our office windowsill "geek garden" (that's what my friends call it!) we have sprouted them under pure fresh, brackish, and even "blackwater" conditions with excellent results! 

Yeah, it would a total shame NOT to incorporate some live Mangrove propagules into the "matrix" you've created! It's really a matter of securing them into the "artificial" root structure, and letting them throw down their live roots and create a "living" component to the aquascape. Keep in mind that it's a slow process, which can take many months to touch down and penetrate into the substrate. Like so many things in our natural-style aquarium approach- patience is key.

And of course, another  fundamental part of the mangrove ecosystem is leaf litter. The leaves which fall from the mangroves form a part of the food web, which encompasses many organisms, from bacteria to fungi, to mollusks and small crustaceans. By incorporating some dried mangrove leaves into your brackish-water aquarium, you can provide both a functional and aesthetic component which has seldom been embraced before in this hobby segment. 

Mangrove leaf litter, like its freshwater counterpart, is the literal "base" for developing our brackish-water aquarium "food chain", from which microbial, fungal, and crustacean growth will benefit. And of course, these leaves will impart some tannins into the water, just as any of our other leaves will!

Much like in our freshwater systems, the mangrove leaves break down over time, providing foraging and sustenance for a great number of organisms, ranging from fungi to our fishes!

And that thing about the tinted water...

Enter the age of the "tinted" brackish-water aquarium.

Yep, tinted. As in "brown."

As in- not your father's brackish-water aquarium. It's not about limestone rocks, quartz sand, and pieces of coral skeleton. Rather, we use combinations of fine sands, muds, leaf litter, and other materials to create a rich, dark, sediment-filled substrate. Possibly creating higher nutrient conditions than typically associated with brackish tanks, yet far closer in step with the rich estuary habitats we're interested in replicating.

Of course "muddy", "nutrient rich", and "tinted", especially in the context of a system with some salt in it, will immediately get you attention from the armchair aquatic warriors of the internet, who will come out of the woodwork to warn you that, "You're headed down a path to disaster!"

This sounds oddly familiar, huh?

Step back from the "doom and gloom" forecasts of naysayers for just a second, okay?

"Nutrient rich." "Tinted..."


This is not only familiar to many of us in the blackwater, botanical-style aquarium's pretty much second nature to us by now, right?

Yeah, tinted, muddy, leaf-litter filled...


And different.

And wide open for experimentation, innovation, and enjoyment. And the biggest obstacle is the act of forgetting our preconceptions about what this type of aquarium HAS been, as presented to us in the past, and looking at what it COULD be when we try this more realistic approach.

Obviously, we should look at tanks that have been created by other hobbyists for inspiration- and I'll keep putting out pics of my tanks to offer some. Yet, I also encourage you to spend a lot of time looking at nature for your inspiration- observe the nuances, the "dirt", if you will- and the potential for replicating it all in the aquarium.

And the fishes? Well, that will continue be a challenge until suppliers/breeders/collectors see a demand for them.

I mean, there are many fishes already in the hobby which can adapt to brackish conditions. There are also many which we seem to have labeled as "brackish fishes", when the reality is that many are found in all sorts of habitats, not just-or not even- brackish. Researching your fishes and their origin is important.

As hobbyists, we're helping to create the market for this stuff, even if we don't look at it from that perspective. The more hobbyists who play with brackish and raise awareness and demand for fishes, the more varieties that wholesalers will bring into the hobby. It's a process...There are a few available right now. Maybe more will come in soon. 

There is a lot to do in the world of the "evolved" brackish aquarium. And it's not just about the look. It's about learning how to care for, spawn, and rear fishes and other animals from this unique environment.Indeed, it's about learning how to recreate and manage the environment in the confines of an aquarium.

Looking for a new frontier to help explore? Brackish just might be the ticket. 

Our focus is on trying to replicate and understand the complex web of life that occurs in brackish water habitats, and we'll evolve the practice and appreciation of this unique niche just like we've all done with blackwater. In fact, the approach that we take to brackish is unlike what has previously been taken before, but one that is incredibly familiar to you as "tint enthusiasts."

It's about husbandry. Management. Observation. Diligence. Challenge. Occasional failure. Yes, you might kill some stuff, because you may not be used to managing a higher-nutrient brackish water system. You have a number of variables, ranging from the specific gravity to the bioload, to take into consideration. Your skills will be challenged, but the lessons learned in the blackwater, botanical-style aquariums that we're more familiar with will provide you a huge "experience base" that will assist you in navigating the "tinted" brackish water, botanical-style aquarium.

It's not "ground-breaking", in that it's never, ever before been done like this before. I just don't think that t's never been embraced like this before...met head-on for what it is- what it can be, instead of how we wanted to make it (bright white sand, crystal-clear water, and a few rocks and shells...). Rather, it's an evolution- a step forward out of the artificially-induced restraints of "this is how it's always been done"- another exploration into what the natural environment is REALLY like- and understanding, embracing and appreciating its aesthetics, functionality, and richness.  

There is still much to learn; much to dismiss as incorrect or unnecessary, and a lot of technique still to develop...

Isn't that fun?

It is.

So, it might be time to say a rather profound "goodbye" to this particular aquarium, but it's time to say, "hello!" to another stage of the journey that will never end.

Our community- you- are doing amazing work- evolving, iterating, and learning new things. Changing minds, and inspiring others. You'll continue to lead the way in breaking through the barriers and facing the challenges which arise when we push into new frontiers.

Stay excited. Stay inspired. Stay bold. Stay diligent. Stay committed...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

July 14, 2021

Hey There,

Great question, and I really don’t have an answer. The Mangrove Oyster, Crassostrea sp., is able to tolerate varying degrees of salinity and exposure to tidal changes. However, it’s a Marien species, and likely isn’t tolerant of extended periods of time at low salinities. Worth doing little research on scholars (not aquarium hobby) sites to find out. -Scott


July 13, 2021

Hi I was wondering if there are any marine clams tolerate lower salinity and conches.

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