Form and function in the botanical-style brackish water aquarium

With the uptick in interest in "Estuary by Tannin Aquatics", we've begun to see some interesting experiments, have had some great discussions, and of course, receive a fair number of questions about the whole idea of botanical-style, brackish water aquariums. And curiously, one of the top questions we receive is how we arrived at the name "Estuary" for our line.

Well, let me explain!

An estuary is the areas of water and shoreline where a freshwater stream or river merges with the ocean. Estuaries can be partially enclosed bodies of water (such as bays and lagoons) where two different bodies of water meet and mix. Hence the whole "brackish" thing. Salinity varies in these habitats, often depending upon tidal influences. And these regions are very ecologically "productive," because of the nutrients brought in by rivers. Many of the fishes and invertebrates that inhabit these brackish water communities migrated from the ocean or freshwater habitats. 

Although aquarists have been playing with brackish tanks for decades, in my opinion, what's been missing is a focus on the actual habitat and how it functions. Just like what the hobby was doing in the blackwater area for years, I think we've been collectively focusing on the wrong part of the equation for a long time- in this instance, just "salt" and basic aesthetics.  

As we've done with Tannin, we're focusing a lot of energy on the functional AND ( far different) aesthetic aspects of the brackish environment than has been embraced before.  Our approach to brackish is a little different than the "throw in a couple of rocks and white sand, a few teaspoons of salt per gallon, add some Monos and Mollies, and you're good to go!" concept that you've seen for a long time in hobby literature. It's not quite as sterile and pristine as the world we've played with before in this sector of the hobby...

To be quite honest, I think that the current "version" of brackish water aquariums is a good part of why they've remained relatively obscure for so long...they are, well...kind of monochromatic, shockingly unrealistic, and dare I say, boring! Sure, there are always exceptions, but the majority of brackish tanks I've seen set up in that manner have, IMHO, left little to generate more than an occasional acknowledgment from the aquarium world at large.

I think we can/will do better.

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."

And of course, there are a few components which, in our opinion, "power" the brackish water, botanical-style system: Mud, leaf litter...and 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 LOVE high-nutrient substrates! 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.

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, 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 ate-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 don't the leaves further.

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).

 I'm really excited about seeing how we develop our brackish water systems, vis a vis the function of the microcosms we foster. I think that the lessons we've learned from our blackwater work will translate very nicely into this slightly salty realm!

Stay curious. Stay experimental. Stay observant...Stay salty...

And Stay Wet!


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


Leave a comment