Brackish water aquariums- from the bottom up!

Want to know a little secret?

Tannin Aquatics almost didn't happen! I came very close to doing something quite different! (I know at least a few "competitors" and people who've tried to copy/rip-off our company recently that would have LOVED that, lol)


There was this other lifelong obsession of mine, which seemed to my friends to be a more logical transition for a geeky aquatics entrepreneur...


Yeah, brackish. As in, brackish water aquariums; mangrove estuaries, intertidal habitats...

I was familiar with these habitats, both as an aquarist and as a traveler, having spent many happy hours in stinky, mosquito-filled tropical backwaters, often knee-deep in mucky soil, poking around the mangroves with the delight that only a fish geek can take!

I had kept brackish tanks for years...a natural compliment to reef tanks; and, at the time, it seemed a good way to transition from the coral world, at least!  I figured that the "Tannin thing" would come later, a natural "digression" from salt-sequentially, if you will. Brackish made sense for someone who had his head firmly in the saltwater world for decades, both as a hobbyist and later, as a business person.

I mean, it wasn't going "all the way" fresh, so it wouldn't have to "wean myself" with as much effort. I developed a brand, product ideas, and all the trappings you'd expect from someone who is totally into something. The aquarium world's first completely dedicated brackish-water vendor. Talk about "niche!"

Yeah, it was pretty serious!

Then I stopped it. Cold.

As you probably have guessed, this "sub-obsession" ultimately morphed into "Estuary", our brackish-water line of natural materials here under the larger Tannin Aquatics "umbrella."

And that's played out pretty well, I think. We've done quite a bit of work with our version of the formerly moribund brackish-water aquarium. One that is dynamic, unique, and altogether different that what has been proferred in years past.

And the whole thing centers largely around Mangroves...

Mangroves are woody plants which grow at the interface between land and water in tropical and sub-tropical regions. Mangroves are what botanists call "halophytes"- plants that thrive under salty conditions. And they do very well in higher-nutrient substrates!

And, like with our freshwater botanical-style aquarium obsession, we'd do well to study these habitats for replication in our aquariums...

In many brackish-water estuaries in the tropics, rivers deposit silt and mud, which generates nutrients, algae, and fosters the development of other small organisms that form the base of the food chain.

This "food chain" is very similar to what we've been talking about in our botanical-style blackwater aquariums. We've spent a lot of time trying to recreate various aspects of food chains in our botanical-style aquariums, and this is a perfect extension of that practice.

The nutrients the mangroves seek lie near the surface of the mud, deposited by the tides. Since there is essentially no oxygen available in the mud, there is no point in the mangroves sending down really deep roots. Instead, they send out what are called "aerial roots" (that's what gives them their cool appearance, BTW), sort of "hanging on" in the mud, which also gives the mangroves the appearance of "walking on water."

And of course, you know that we have a more than "casual" interest in substrates, right? The composition of the substrates where mangroves reside is very interesting, and as aquarists, we'd do well to refer to some studies of these habitats.

Mangrove soils are an interesting, nutrient-rich mix of marine alluvium, transported as sediment and deposited by rivers and the ocean tides. Soils are made up of sand, silt and clay in various combinations. Mangrove soils are typically saline, anoxic, often acidic and frequently waterlogged.

A real "cocktail" of variables, right?

You often hear the substrate in these habitats referred to as "mud." In this context, of course, "mud" actually refers to mixture of silt and clay, both of which are rich in organic matter. The "topsoil" is a combination of sand or clay. Now, interestingly, the lighter-colored topsoils, consisting largely of sand, are pretty well aerated. The clay-like topsoils are far less aerated.

In a recent study of these habitats which I stumbled on, the researchers concluded that the composition in typical mangrove habits was as follows: "Overall sediment proportion of main fractions is 59% for silt, 21% for sand and 20% for clay."

Of course, this has some implications for those of us who are trying to recreate this type of habitat in our aquariums, doesn't it?

Mangrove habitats are usually enclosed and protected environments, with low-energy waters, which is conducive to sedimentation of clay particles. Now, confusing the matter further is that various studies of tropical mangrove forests worldwide have revealed that mangrove soils may be either acidic or alkaline, depending upon the materials deposited within them. 

In mangrove soils, nitrogen is considered the primary nutrient that affects species composition and mangrove population density. Further analysis found that nitrogen and phosphate influence structure and composition in approximately equal proportions. Potassium is beneficial for mangrove growth, yet vitally important in higher salty environments, as it impacts the osmotic regulation that occurs within the mangroves themselves. So, if you're keeping mangroves in very salty conditions, dosing a fertilizer containing potassium might be quite beneficial!

Now, we talk in general terms about mangrove soils being "nutrient rich"- and they are, for the most part. However, there are significant variabilities because of the dynamics of the mangrove habitat. Although some mangrove soils have extremely low nutrient availability, this factor varies greatly between mangroves- and also within a mangrove stand! In other words, the mangroves themselves actually influence these factors! 

In general, it's understood by ecologists that nutrient-rich silty sediments produced faster growth of mangrove seedlings- vital in this important ecosystem- and of extreme interest to those of us who wish to sprout and grow mangrove propagules in the aquarium!

And of course, the leaves which mangroves regularly drop form not only an interesting aesthetic and "structural" component of the habitat (and therefore, the aquarium!)- they contribute to the overall biological diversity and "richness" of the habitat. 

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 mangrove habits, stimulate phytoplankton growth there. 

Interesting, right?

Yeah, leaf drop is a big deal in mangrove habitats! And this phenomenon is something we can- and should- replicate in our aquariums!

The high level of carbon "allocation" to roots of mangroves, in conjunction with mangrove litter fall, and the rather low rates of decomposition which occur in anoxic soils, results in mangrove ecosystems being quite rich in organic matter. And despite these lower rates of decomposition, the mangrove leaf litter is a major source of nutrients in the mangrove ecosystem!

Yeah, leaves again!

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 don't the leaves further.

And of course, higher organisms like shrimp, crabs and mullosks are the dominant organisms in these ecosystems, performing an important role in "processing" leaves and other organic materials which accumulate in them.

Organisms found in mangrove habitats are referred to as either "epifauna" or "infauna", and they perform different roles within the ecosystem. "Epifauna" refers to those invertebrates that live on various substrates such as lower tree trunks and the sediment surface, but which do not burrow into it. Gastropods, crabs, and bivalve species are typical representatives of the epifauna in mangrove ecosystems. "Infauna" refers to burrowing invertebrates, which live within the sediment, and includes crabs, shrimps, polychaete and sipunculid worms.

And then, there are the fishes, of course.

So yeah, we love the idea of creating your brackish water ecosystem around leaves and mangroves (either alive, or just utilizing the roots/branches to simulate the appearance of the mangrove root system). The possibilities are endless for creating fascinating aquariums and unlocking some cool secrets!

Those of you who have experience with both aquatic plants and botanical-style aquariums will really enjoy our interpretation of the brackish water habitat. And, if you're also a marine aquarist, that "skill set" can only help, too! 

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 (2.5 years) in Tannin's existence, as we were just starting to venture out and unlock some secrets in the blackwater/botanical game...But I think that the two can continue to develop together and spur on new hobby advances.

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

So, if you were contemplating playing around with this whole brackish water/botanical-style aquarium game, it's a really good time to experiment! We're looking forward to seeing more an more of your experiments and ideas coming to this tinted, slightly salty world!

Stay curious. Stay resourceful. Stay bold. Stay excited. Stay adventurous. Stay creative. Stay enthusiastic...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


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