August 17, 2017

It happens in the "mangal"

With interest starting to increase in the brackish-water, botanical-style aquarium, we're seeing a lot more questions about the habitats and ecological niches where our fishes come from. In particular, a lot of you are curious about the mangrove communities known as "mangals." First off, a "mangal" is a term for "mangrove swamp", derived from Arabic. It's the name most commonly associated with these unique communities.

As we've discussed before, one of the defining characteristics of these mangrove communities is that they are located where fine sediments (often with high organic content) collect. They are host to a variety of organisms, ranging from algae to oysters, and continue to attract sediments in their matrix of roots. Fine, anoxic sediments under the mangroves act as "sinks" for a range of compounds, including heavy metals, and nutrients such as nitrogen and phosphorus, deposited into estuarine waters from terrestrial sources.

Because many of the mangals are intertidal- connected to the ocean and subject to tidal fluctuations, Mangroves are, by necessity, hardy plants, and can tolerate a significant, fluctuating range of salinity, temperature, and moisture, as well as a number of other varying environmental conditions. This adaptability has made them extremely successful ecologically.

And most interesting to us as fish geeks, many fish species spend their juvenile stages in the mangals, deriving food and protection from the vast mangrove root systems. And of course, there are a variety of fishes which spend their entire lives in these unique habitats. Some, such as species of killifish and mollies, are familiar to us, while others, such as many gobies, Rainbowfishes, and even cichlids, may be somewhat less familiar. I the coming months, we'll spend more time looking at some of the aquarium-suitable fishes which occur in the mangrove habitats.

One of the defining "ingredients" of a mangrove habitat is the sediment and mud which comprise the substrate. There are a number of ways to replicate this in the aquarium, which include utilizing combinations of commercially-available sands, muds, and sediment mixes specifically intended for aquarium use. You can also experiment with terrestrial soils, such as those used by "dirted" planted aquarium enthusiasts.

Now, to clarify our "Estuary" vision of the botanical-style brackish aquarium for a second, it should be noted that we support the use of both living and non-living materials to create both a functional and aesthetically-unique display.

We like to use dried mangrove branch wood and root sections to create the "foundational hardscape" of the aquarium, and then, enhance this by securing live mangrove propagules into the matrix. As they put down their famously long and complex roots, they will eventually "find " the substrate.Or, if you prefer, you can plant them in a fine, rich substrate from the start. They simply need to be partially submerged, and provided with bright illumination from a variety of sources.

Once they start growing leaves, you will need to spray them with fresh water from time to time to keep them from drying out and becoming caked with salt, which they release through the leaf tissues. As part of their growth, they will drop leaves from time to time, which, in our book- is a pretty cool thing, as this contributes to the biological "richness" of the aquarium as the leaves decompose! And of course, we recommend using dried mangrove leaves on the substrate, as you would in a blackwater aquarium, to further enhance this "richness!" Now, the rich substrate we advocate will also be beneficial to a variety of aquatic plants, so using specimens like Cryptocoryne ciliata and others will take advantage of this richness.

With all of this wood and sediment, it seems like we're advocating a pretty rich, higher nutrient environment, and that's correct! Your water will likely take on a tinted appearance, of course, and this is likely contrary to your previous experience with brackish-water systems, where the aesthetic was clear water, white sand, and rocks. We're advocating what we feel is a more realistic, functional, and more productive system for a wide variety of organisms. And, like it's blackwater counterpart, the brackish water, botanical-style system will require some monitoring of the water parameters and regular husbandry (i.e.; water exchanges, etc.) to help maintain a stable, healthy environment.

From a purely aesthetic standpoint, the mangal can be recreated by vertically-orienting mangrove branches and roots in a deep substrate. And you have many options. If you're using a tall, narrow aquarium or a cube, you can simulate the dense matrix of the root system and the accompanying life which inhabits it.

Or, if you like, you could employ a standard rectangular, or wide aquarium and a single mangrove root aggregation on one side, to represent the area at the "margin" of the mangroves, or you could do a riparium-style tank, with a "shoreline" built up, and the mangrove roots and the planet themselves positioned accordingly. Lots and lots of possibilities for different approaches. We're excited about the ability to use traditionally more "annoying" cube-type tanks for unique applications!

Since we're talking about brackish (1.003-1.005 is our target specific gravity), you have options to adapt a lot of different fishes to this habitat. Now, if you're really adventurous, you could gradually "evolve" your aquarium to a full-strength marine environment (like 1.021-1.025) and add some interesting marine fishes, like Pipefishes, Dragonets, Seahorses, and various gobies and Damselfishes into the mix. And of course, you could begin adding some hardy corals, like Xenia, Ricordea, Pocillopora, etc., and ultimately, some "LPS" corals like Goniopora and Trachyphyllia. Oh, and Seagrasses and/or macro algae! This would be an interesting way to start a most atypical marine aquarium!

The idea of a botanical-style brackish aquarium is to create a "platform" for all sorts of life, with the option to go in a variety of directions. In my opinion, the formerly sort of "drab" and one-dimensional brackish tanks of the past can give way to a more flexible, adaptable, and highly dynamic aquatic microcosm that can evolve into what might be one of the most diverse and amazing ecosystems you could imagine! The potential to unlock some secrets on "both sides of the salinity line" is irresistible, and the opportunity for experimentation is wide open to the intrepid hobbyist!

As more and more of our community begin working with this "methodology", the "state of the art" will definitely evolve, with techniques, ideas, and even aesthetic "styles" changing regularly. It all starts with the "mangal", and wolves from there!

We encourage you to come along for the ride!

Stay excited. Stay enthusiastic. Stay creative.

And Stay Wet.

Scott Fellman

Tannin Aquatics