March 26, 2019

Interpreted Nature and the bounty that is brackish...

We've played around with the idea of what I've called "evolved" brackish tanks for some time now. I know, the term "evolved" might actually sound a bit pretentious, I suppose- but I think it describes our approach pretty accurately. Allow me to digress for just a minute or two.

Traditionally, in the aquarium hobby, when you've mentioned that your thinking of trying a brackish water aquarium, it's provoked little more than a raised eyebrow or a feigned level of interest from fellow fish geeks, and I kind of can see why. Although aquarists have been playing with brackish tanks for decades, in my opinion, what's been missing is a focus on the actual habitat we are interested in, and how it functions.

Functional. Yeah.

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- just "salt" and basic aesthetics. And quite honestly, the hobby "knowledge base" on the wild brackish water habitats and how dynamic, interesting- and yeah, awesome-looking they are has been sadly lacking.

Brackish water (arguably possessing a 1.005-1.010) is a sort of "middle ground" that for decades in the hobby has been well-travelled, yet widely mis-understood. I've played with brackish water for almost two decades, in between reef keeping and my blackwater stuff, and in researching both the hobby work that has been done, and relevant scientific papers out there on the wild habitats, have sort of made this conclusion that it's simply been an afterthought, at best for aquarists.

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 of course, that's why we launched "Estuary", our little foray into the brackish water aquarium "sector" (of which there isn't one, FYI).

Our approach to brackish has be 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! Brackish biotope" idea that you've seen for a long time in hobby literature.

As you suspect, our approach is to really take a look at the function and appearance of these unique aquatic habitats, and then construct aquariums which mimic these factors in a unique and more compelling way. To do this, we want to really focus on helping you replicate and understand the complex web of life that occurs in brackish water habitats, and how you can replicate parts of it in the aquarium.

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 already quite familiar to you as "tint enthusiasts."

A system that embraces natural processes and functionality...And just happens to have a different aesthetic, too! 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, and stained a bit from tannins. Beautiful in a very different, yet oddly compelling way. A "tinted" brackish water aquarium.

And it all starts with the Mangrove.

Mangroves, which grow at the water's edge, have roots that are either submerged or very wet most of the time, which makes them the perfect habitat for all sorts of aquatic life forms- mussels, oysters, crabs, fishes, etc. They draw oxygen from the air through small areas of spongy tissue on their bark.

I've been obsessed with these trees for years. I was the guy who, on a surf trip to the South Pacific, would bring along his dip net and a swing-arm hydrometer to wade into some insect-infested, sometimes smelly, decidedly nasty muck to conduct a little amateur "field research" in between surf sessions, much to the chagrin of my travel companions!

Yeah, I did get a few bug bites from time to time. Worth it. I mean, what's not to like about mangroves? And seeing them in context is a huge thing for the natural aquarium enthusiast!

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 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: fungi, bacteria, and epiphytic life forms.

They're simple to sprout from seed pods, known more accurately as propagules. We'll discuss the handling, securing, and sprouting of mangrove propagules in the aquarium in a future piece.

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."

We're just scratching the surface here on mangroves, and in a future piece, we'll touch on the optimum ways to sprout and grow these fascinating plants in aquariums.

And of course, where you have trees- you have leaves. And where you have mangroves...you have mangrove leaf litter! We've offered the dried leaves of the Red Mangrove (Rhizophora mangle) for a couple of years now, and it's proven justifiably popular with our community, much in the way catappa and guava have.

Mangrove leaf litter facilitates the growth of these bacteria, fungi, and other life forms which contribute significantly to the aforementioned food chain in both the wild and the aquarium. Allowing it to accumulate, decompose, and contribute to the biological richness of our brackish-water aquariums is part of the charm and fascination with these systems!

Oh, and it adds a tint to the water!

And, since we're talking about materials accumulating on the substrate, let's touch on the composition of the substrate.

There is a lot to be learned from the composition of the substrates in which Mangroves grow, much like we've learned about blackwater substrates in our journeys...In many habitats, the "mud layer" is actually peat ( as much as 3 meters deep, in some instances!) overlaid with a shallow (0.5 m) layer of sand. Mangrove soils with a high content of organic matter are very common. (I think that planted aquarium hobbyists can be a huge help in understanding and evolving the materials we need to recreate this habitat in our tanks, BTW.)

In my personal brackish water aquarium, I've assembled a substrate which is both interesting to look at and mimics, to some extent, the composition and function of those found in the wild. I realize that, for many hobbyists, using "straight-up" mud in your tank is going to be challenging at best, disastrously messy at the worst, so I utilized less "tempermental" materials to construct mine.

I started with two of one of the finer, commercially-available marine "biosediment" products- one by CaribSea, the other by Kent Marine. These were substrate materials that were formulated to mimic the mineral composition and substrate size of the materials found in these unique habitats. Love these products!

The average particle size of the minerals used in these formulations is similar to the natural reef sediment composition present in reef flats, seagrass beds, mangrove estuaries, and lagoons. (All of which, by the way, are epic habitats that any fish geek should consider replicating in his/her aquarium!)

I mixed in a small amount of pond soil into the biosediment materials, to give the mangroves some good "nourishment" when the roots "touch down." I also mixed in some planted aquarium substrate (ground up a bit) for the next layer. For this, I incorporated Ultum Nature Systems "Control Soil"- a product that I've been pretty obsessed with in my freshwater work to mimic the natural substrates of flooded forests.

Hey, should we offer this stuff on our website? Let us know!

Continuing on, we topped our substrate with Carib Sea "Sunset Gold" sand, to create a somewhat brighter look which mimics the appearance and structure of the natural estuary ecosystems. It's the perfect "topper" for a rich and varied substrate!

And I've heard the "warnings" from people on attempting to replicate the habitat in this manner 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 and unstable!"

Etcetera...

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

Just like when we started sharing our vision of a botanical-style aquarium (blackwater or otherwise), we heard plenty of protestations, warnings, and critiques from both well-meaning and not-so-well-meaning hobbyists alike-many of whom never even kept a brackish tank themselves. And hey, it's great that we look at stuff critically. However, we also need to follow our instincts and feel free to experiment and play our hunches. Risks are always present. Yet, taking risks in the face of critics is one way we advance in the hobby.

And there is sooo much more to discuss here. We haven't even touched on the fishes and other organisms you can keep. I'm simply trying to tempt you with teasers about the cool environment we hope to see you replicate!

More to come.

Stay salty. Stay curious. Stay creative. Stay excited...

And Stay Wet.

Scott Fellman

Tannin Aquatics