The continuing saga of my semi-salty obsession...

Like many of you, I find it hard to stick to just one obsession in the aquairum hobby. As you probably know by now, I have had a long term love affair with the brackish water habitats of the tropical world. 

There are a lot of misconceptions about brackish water aquairums floating around out there. And the hobby interpretation of brackish water habitats has impacted not only the technique, but the aesthetic interpretation of these habitats as well. 

Although there is a good amount of information on brackish-water habitats from which brackish water fishes come, in the hobby, (with the rare exception of some biotope enthusiasts) we've sort of distilled brackish water aquarium aesthetics down to white aragonite sand, a few rocks, and maybe some hardy plants...and it's been mired in that aesthetic hell for decades.

And then there is that "perception" thing...

I think that the perception among many aquarium hobbyists was that brackish is more tricky to keep than freshwater, and easier than a reef tank, yet offers little in the way of excitement on first glance. I mean, the fish selection and availability has not been exactly stellar, with many dealers hesitant to stock brackish fishes for simple lack of demand and interest.

And quite frankly, many fishes that have been perceived to be "brackish" by hobbyists are either actually from pure freshwater habitats (I'm thinking about certain Glassfish and some Rainbows), or have some populations that are from brackish (which are seldom imported).

And then there are those fishes, like Mollies. which are Euryhaline (capable of tolerating a wide range of salt concentrations), with the majority being found in pure freshwater. Salt, in many cases, is simply used for health purposes.

(P. sphenops by Hugo Torres. Used under CC by 2.5 es)

Oh, and I can't even begin to tell you the challenge I went through to source a group of Bumblebee Gobies that were actually collected from a brackish water habitat! And even then, the species ID on mine is not 100%; with a few hobbyists insisting that mine are a pure freshwater species...and of course, when I do the research, I discovered that there are populations from both pure fresh AND brackish,,,Arrghhh!

One of the biggest differences between the botanical-style approach to brackish aquariums and the more traditional approach of "rock and crushed coral/oyester shell, etc." approach is that there are a variety of natural collateral benefits to the physical environment that you can realize by having materials like mangrove root sections, branches and leaves in the water.

Use of mangrove roots, branches, and leaves virtually assures that you're going to be imparting tannins into your aquarium water.  The tannins, of course, not only add an appealing visual "tint" to the water, they provide other benefits as well. In this instance, tannins realized from the mangrove wood and leaves will react with calcium and other alkaline compounds to produce the insoluble salt, calcium tannate. The by-product of this reaction is the releasing of calcium and other ions into the water, which serve to buffer the pH in the aquarium.

So, yeah, oddly, having a bunch of wood and leaves  in your tank will actually create a sort of stability that benefits your tank in ways you may not have considered!

Of course, that's just a water chemistry benefit. There are many biological benefits to this approach, as we've discussed before.

The hardest thing we've had to do- and continue to do- is to change the perception among hobbyists that brackish water biotopes are stark white sandy places with a few rocks, and super clean water. Actually, many brackish water estuaries and lagoons are way different than we've portrayed them in our aquariums over the years.

Mud, leaf litter...and mangroves.

They are often turbid, brown-tinted waters, with muddy, rich bottoms covered with decomposing leaves, lots of micro and macro algae, some plants, and often dominated by Palms and Mangroves. 

Sometimes, you'll find amazing mangrove growth in blackwater ecosystems, more reminiscent of the types of habitats we're used to replicate in our aquariums!

Yet, the aquairum world has its quirks...and opinions- about how things should be...

Over the years, I've heard the "warnings" from people on attempting to replicate this habitat in the aquarium:

"It won't work in a brackish tank! It will create anaerobic conditions! Too much nutrient! Ionic imbalance...Tinted water means dirty!"


Man, this sounds oddly familiar, doesn't it?

A lot of naysaying, without a lot of actually trying. "Regurgitation Syndrome" rears its ugly head again.

And, yes, the by-product of our approach is that it just happens to have a different aesthetic, too, by virtue of the materials we work with. Less emphasis on "sterile" white sand and crystal-clear water, and more emphasis on a functional representation of a tropical, brackish water ecosystem: Muddy, nutrient-rich substrate, filled with decomposing mangrove leaves, and stained a bit from tannins. Beautiful in a very different, yet oddly compelling way.

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.  

"Richness." A good word. actually.

The bottoms of this type of habitat- and the aquairums which represent it-are covered with a thin layer of leaf litter. Specifically, mangrove leaf litter. This not only provides an aesthetically interesting substrate- it offers functional benefits as well. Like, imparting minerals, trace elements, and organic acids to the water.

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!

Fungi and bacteria in brackish and saltwater mangrove ecosystems help facilitate the decomposition of mangrove material, just like in their pure freshwater counterparts. Interestingly, in scientific surveys, it's been determined that bacterial counts are generally higher on attached mangrove leaves than they are on freshly-fallen leaf litter, and this is kind of interesting, because ecologists feel that attached, undamaged mangroves leaves don't release much tannin, which, as we know might have some anti-bacterial properties. However, it's also been found that materials like humic acid, which are abundant in the mangroves, stimulate phytoplankton growth there. 

Interesting, right?

The leaves of mangroves, as they break down, become subject to both leaching of the compounds in their tissues, as well as microbial breakdown. Compounds like potassium and carbohydrates are commonly leached quickly, followed by tannins. Fungi are the "first responders" to leaf drop in mangrove communities, followed by bacteria, which serve to break down the leaves further.

So, in summary, you have a very active microbial community in a brackish water aquarium. 

The management of a brackish tank is really surprisingly similar to that of a typical blackwater aquarium. The biggest difference is the salt and perhaps a greater interest in a rich substrate. Now, one parameter that hobbyists will argue about is specific gravity. I tend to favor one of two specific gravities in my brackish tanks: 1.005 or 1.010 I've changed over the past few years, having tried all types of ranges, from as low as 1.004 to 1.008. Finally, I settled on 1.010, because  it is a sort of "sweet spot" that many of the brackish water fishes which I am interested in (gobies, rainbow fishes, mollies, etc.) seem to fare quite well at this slightly higher S.G.

And the mangroves don't seem to have any problem with that, either!

Oh, let's talk about mangroves and detritus again...

One of the first decisions I made when I started to apply botanical-style aquarium "methodology" to brackish was to NOT siphon out the "organic debris/detritus" (total "catch-all" phrase, huh?) that accumulate during the normal course of existence of any aquarium. My rationale was that, the bulk of this material was fish waste and broken down leaves and botanicals, as opposed to uneaten food and such.

My whole point of the brackish water/Mangrove aquarium "exercise " is to create a simulation of the organic-heavy, exceedingly rich substrates in which they are found, while still creating a manageable closed system that doesn't turn into a cesspool!

I kind of figured that I don't overfeed. I don't over-stock, and I perform regular water exchanges on a weekly basis. I employ practices which assure as much environmental consistency as possible. And yeah, the physical environment in my brackish water mangrove tanks have a very slight amount of fine organic debris/detritus on the substate.

I've purposely siphoned the stuff out before, and by crude estimation, I'd say that well over 80% of what there actually is there, accumulating on the substrate, is the aforementioned botanicals and leaves In a decomposed state.

A sort of "mulch", if you will. I do see Nerites snails and some of the fishes foraging in this material from time to time... but it's not all that noticeable unless you look really carefully.

I think these replicate, to some extent, the types of rich substrates in which mangroves grow and thrive. If you recall from my previous ramblings about this approach, we long ago decided to abandon "clean white sand" in favor if a "compound" of fairly rich substrate materials, including "marine biodsediment" , soils,  and aragonitic sand, and occasionally, a more coarse aragonite for the "top-dressing" of sorts.

We've been using this successfully for years, and it'll soon be released under the name, NatureBase "Mangal" on our site. We think you'll love it, too!

The reason for this selection of "rich" substrate materials back in the day was twofold:

First, I wanted to create a functional mud-like substrate that would facilitate both denitrification and the ability to  provide a habitat for minute life forms. I felt that this would also be a more natural setting for a brackish water aquarium.  I knew that mangroves would love it. My original intent, years ago, was to plant some Cryptocoryne ciliata, a species well-known for its ability to adapt to a low salinity brackish-water environment in my tanks.

This plan was ultimately abandoned when I decided to increase the specific gravity of the aquarium to 1.010, considerably higher than the documented SG at which this plant is known to survive (typically 1.002-1.005). Plus, it was a pain in the ass to find that damn Crypt!

And mangroves are way cooler, anyways.

There is a certain faith you need to have in employing such a rich substrate in a aquarium even before anything is physically rooted in it, As you know by now, mangrove propagules put out roots whenever they're damn ready, and then- and only then, do the roots make contact with the substrate. You can't shove a rootless propagule into the sand and expect it to sprout. I knew from a lot of time playing with mangroves in reef systems that his process takes many months, of course, given the depth of the tank.

Patience is mandatory.

If you ARE patient, you'll be rewarded. It'll take months, but your mangroves will do what they do in Nature: They put down prop roots, and grow many leaves, some of which dry up and fall...and of course, we do allow the leaves to accumulate on the bottom, just like in the natural habitats we are attempting to replicate to a certain extent.

Mangrove ecosystems are remarkably complex, diverse systems which process nutrients by decomposing and utilizing organic matter. Many organisms, like fungi, bacteria- even sponges, work together to utilize the vast food resources produced in these habitats. And larger creatures, like crabs, amphipods, etc., break apart leaf bits, providing a "gross dismantling" service that contributes to decomposition of these materials, leading to detritus.


Yeah, if you want to move beyond the absurd, hyper-santized hobby version of a brackish water aquarium, you need to understand how these ecosystems work, make some "mental shifts" to accept the appearance, the challenges, and the obligation to observe, test, and maintain these systems over the long haul. And you need to deploy, as with anything we do- a shit-ton of patience.

Up for it?

You can do this. Easily.

Get to it. You can contribute a lot to the ever-evolving world of the botanical-style brackish water aquarium! Join us. We're there waiting for that "delta of the intersection between science and art..."

Stay inspired. Stay curious. Stay patient. Stay brave. Stay resourceful...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


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