A salty "sayonara"- or a shift to the future?

As we're entering into the final phases of the brackish water aquarium we set up in  our office more than a year and a half ago, it's time to sort of reflect upon the lessons learned and the joys of the journey.  My decision to take this tank down was very difficult- and only made because it was time to use our limited tank space here to show you something different. I love this tank.

Over the operational lifetime of this tank,  I've noticed some interesting things about the way this tank runs, and how it is so similar to the blackwater systems we're all familiar with by now.

Like our "conventional" (Shit, that's funny to say, huh?) botanical-style systems, the brackish system embraces the same use of decomposing leaves, wood, and botanicals, with the added variables of a rich, "sediment-centric" substrate and the dynamic of specific gravity to contend with. 

Interestingly, however, this type of system runs much like the blackwater, botanical-style systems that we are used to, with the exception that it is far more "nutrient rich" than the blackwater tanks. The dynamics of decomposition and the ephemeral nature of leaves and such in the water are analogous in many respects, as well.

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!

And yeah, the water in a brackish system "configured" in this manner is decidedly tinted- largely a function of the mangrove branches and roots, which, as they break down, give off a significant amount of color-producing tannins from their tissues.

It's hardly a secret that mangrove wood, leaves, and bark are loaded with these tannins! In fact, Red Mangrove bark is one of our favorite "secret weapons" for producing incredibly deep tint in all types of aquariums!

The management of a botanical-style 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 deep, very rich substrate. Now, one parameter I changed since the system began was to increase the specific gravity from 1.004 to 1.010 This was done because it is a sort of "sweet spot" that many of the fishes which I am interested in (gobies, rainbow fishes, chromides, mollies, etc.) seem to fare quite well at this slightly higher S.G.


Also, I've made no secret about a desire at some future point to do a brackish system where I slowly push things all the way up to like 1.021 (on the low end of natural seawater specific gravity) and incorporate corals and macro algae into the display, along with marine fishes! And, if I do execute this, the "creep" towards this higher S.G. will be made over a very long period of time (close to a year), so it will be advantageous for the resident fishes to adapt to full-strength marine water slowly. 

So, yeah, you're playing with salt...

Do yourself a favor and splurge on a digital refractometer. Not a "swing arm" hydrometer that breaks easily and goes off-calibration if you look at it wrong, not a conventional refractometer which forces you to "read between the lines" to obtain an accurate reading. No. Splurge on a good piece of gear-spend over one hundred dollars and get a real-deal, name brand piece of lab-quality equipment that will give you precise readings with a minimum of hassle and will last for years...

Do it. You won't regret it at all.

And sure, managing a system that "floats" between two realms (freshwater and marine) seems like a bit of a balancing act, I know..because it is. However, it's not difficult. You simply apply the lessons you've learned playing with all of this crazy botanical-style blackwater stuff we talk about all the time.

Yes, you might kill some stuff, because you may not be used to managing a higher-nutrient brackish water system. You have a number of variables, ranging from the specific gravity to the bioload, to take into consideration. Your skills will be challenged, but the lessons learned in the blackwater, botanical-style aquariums that we're more familiar with will provide you a huge "experience base" that will assist you in navigating the "tinted" brackish water, botanical-style aquarium.

Now, this IS a different type of approach to brackish aquariums. 

However, it's likely not "ground-breaking", in that it's never, ever before been done like this before. I just don't think that t's never been embraced like this before: Met head-on for what it is- what it can be, instead of how we wanted to make it (bright white sand, crystal-clear water, and a few rocks and shells...Nature "edited" to our aesthetic "standards"). Rather, 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.  

I'm proud to have pushed this type of approach, and even prouder that many of you have been inspired to try it as well!

Figuring out how to bring this into our aquariums. That sort of thing.

What really sets our approach apart, besides simply the aesthetics of it all, is the function- which is a "by-product" of us going more "natural" and modeling our aquarium after the actual habitats themselves.

The bottom of this type of habitat is covered with a thin layer of mangrove leaf litter- and of course, that's part of the attraction here! This will not only provide an aesthetically interesting substrate- it will offer functional benefits as well- 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!

And you can play with many different types of substrate materials, ranging from sand to mud and everything in between. The richer the better, as far as I'm concerned. 

And of course, no brackish water aquarium is complete without brackish-water fishes...And traditionally, that has been a bit of a challenge, in terms of finding some  "different" fishes than we've previously associated with brackish aquariums. I think that this will continue to be a bit of a challenge, because some of the fishes that we want are still elusive in the hobby. New brackish-water fishes will become more readily available when the market demand is there. In the mean time, we can focus on some of the cool fishes from these habitats which are currently available to us.


However, one of the things I've found is that you need to go beyond "what the hobby articles say" and look into actual information from scientific sources about the types of habitats our target fishes actually come from. There is still a surprisingly large amount of misinformation about there concerning fishes long thought to be "brackish", when the reality is that they are often found predominantly in non-brackish habitats, with perhaps only isolated populations of fishes being brackish fishes.

And of course, the real "stars" of the show, IMHO, are those mangroves! Let's get back to them for just a few minutes...

Specifically, the "Red Mangrove", Rhizophora mangle. The one we'll focus on here and refer to as "Mangrove" for the purpose of this piece.

Hardly what you'd call an "aquarium plant"- I mean it's a tree.

That being said, the Mangrove is an amazing tree that certainly has applications for aquariums- specifically, brackish aquariums. Now, without going into a long, long, recap of what mangroves are and how they function (You can Google this stuff and get hundreds of hits with more information than you could ever want), let's just say that mangroves are a group of trees and shrubs which live in the coastal intertidal zone, in areas of warm, muddy, and salty conditions that would simply kill most plants.

They possess specialized organs which allow them to filter out sodium, absorb atmospheric air through their bark, and generally dominate their habitats because of these and other remarkable adaptations.

There are about 100-plus different species, all of which are found between tropical and subtropical  latitudes near the equator, as they are intolerant of cold temperatures. Mangroves put down extensive "prop roots" into the mud and silt in which they grow, giving them the appearance of "walking on water." These root tangles help them withstand the daily rising/falling tides, and slow the movement of the water, allowing sediments to settle out and build up the bottom contours of the local ecosystem.

And of course, the intricate root system not only protects coastlines from erosion, it plays host to a huge variety of organisms, from oysters to fungi to bacteria  to fishes. The fishes use mangrove habitats as a feeding ground, nursery area, and a place to shelter from predators.

Okay, you get it. But how do we use these trees in the aquarium. And wait a minute, you're talking about a tree? WTF?

I have no illusions about using live Mangrove plants (available as "propagules") to serve as "nutrient export" mechanisms as they do in nature. You've seen this touted in the hobby over the years, and it's kind of silly, if you ask me. They just grow too damn slow and achieve sizes far beyond anything we could ever hope to accommodate in our home aquarium displays as full-grown plants with large-scale nutrient export capabilities. We've played with this idea in saltwater tanks for decades and it's really more of a novelty than a legit impactful nutrient export mechanism.

Mangroves can and will, however, reach a couple of feet or so in an aquarium over a number of years, and they may be "pruned" to some extent to keep them at a "manageable" size, similar to a "bonsai" in some respects.

You've probably figured out by now that I'm a huge fan of mangroves!

Well, yeah. I am.

Oh, and before you part going off on me about their unsuitability for aquariums or some ethical implications for their "removal" from the wild, let's talk for a second about how we acquire them and how they grow. First off, removing a growing mangrove tree or seedling from the natural environment is damaging, unethical, illegal in most areas, and essentially idiotic.

NO one should even consider doing that. Period.

Rather, we acquire mangroves as propagules- buoyant seedlings which grow through the fruit, and can produce its own food through photosynthesis. When the propagules are mature, they fall into the water, and can remain in a dormant state, withstanding desiccation, for more than a year! Propagules are buoyant and can float until they find suitable "anchorage." When it's ready to take root, a propagule will change its internal density to float vertically, rather than horizontally, to make it more likely to root in suitable sediment. 

As aquarium people, we start with these free-floating propagules, which are abundant and legal to collect in places like Florida, where the adult plants are protected from harvest or pruning. They're often found washed up on beaches throughout their range. The advantage of propagules is that they can be stored in a moist environment and easily shipped in damp paper towel, and stored that way for extended periods.

So, once you have one of these pickle-like propagules, how do you use it?

First off, you don't need to "root" it, or "plant" it in substrate. You simply need to anchor it in the water column in a vertical position, and allow it to extend roots down towards the bottom on its own pace. I have typically done this in relatively small containers of water, like a jar, vase, or pitcher, before translating it to the aquarium. 

You'll know that the propagule is ready to transplant when it becomes a "seedling"- with little roots showing up on the bottom, and leaves beginning to unfurl on the top of the propagule. You can sprout the propagules in all sorts of light conditions- typically even room ambient lighting (as in a windowsill) will do the trick.

Fluorescent, LED, or other aquarium-rated "daylight" lighting will accomplish this, too. Of course, the part with the leaves needs be anchored above the water line (yeah, people ask me this question regularly). Like everything we do in the "natural-style" aquarium game, patience, diligence, and observation are essential when keeping Mangroves.

If using an artificial light source, be sure to mount the light well above the container or aquarium where the mangroves are kept. This not only results in a more natural-looking growth form- it keeps the leaves from growing literally right into the light and frying themselves (I've done that many times, lol).

Once they are placed in the aquarium, you should anchor them near the water surface, not in the substrate. As discussed many times before, I've chosen to attach my propagules to (legally-collected) mangrove root pieces in my brackish- water aquarium, and that works really well.

Allow the roots to "find' the bottom for themselves. This will encourage the growth of a strong, almost "woody" prop root system that these trees are famous for. It may take many months for them to achieve "touchdown and penetration" into the substrate, but they will- and a stronger plant ensues as a result of allowing them to do it themselves!

One little word of advice: Be sure to sprout your mangrove propagule in the same water conditions (ie; marine, brackish, fresh) as you will be keeping them in perpetuity in your aquarium. They categorically don't adapt well to habitat changes once they have begun to grow.

Of course, we need to go back to talking about substrates once more. Keep in mind they come from muddy, sedimented, nutrient-rich environments in Nature, so they can handle just about anything. I've personally utilized everything from marine biosediments to aragonitic sand, to mixes of pond soil or aquatic plant soils. You can mix in peat and all sort of substrate enhancement materials to provide sustenance and proper rooting for these hardy trees. A little online research can yield lots of great tips on substrate mixes for mangroves in the captive environment.

The beauty of mangroves is that they're pretty hardy and generally adaptable- which bodes well for their care in the aquarium! You need to do little more than illuminate them, anchor them in a vertical position above substrate, and mist the leaves on a regular basis. This process helps to keep dust, salt build-up (which is exported via the leaves), and insects off of the leaf tissues.

Now, again, we hear arguments that keeping a tree in an aquarium is kind of crazy.

I admit, a full-grown mangrove tree is virtually impossible to keep in a home aquarium. However, these trees grow incredibly slowly, reaching "houseplant-like" sizes after a year or more in captivity. And, with frequent pruning, you'll see that they can be maintained in almost a "bonsai-like" size indefinitely- all the while putting down the extensive, intricate  root systems that they are so famous for.

Yes, I'm repeating myself here, but . I really want to emphasize that point.

One of the cool benefits of mangroves in the aquarium- just as in Nature- is that their roots will recruit and foster the growth of microorganisms, fungi, algae, and other epiphytic life forms, providing a foraging place for fishes, and the ability to contribute to the biodiversity and healthy function of your aquarium ecology.

In addition, the "leaf drop" which mangroves are known for accomplishes the same thing it does in Nature, too! It encourages the growth of microorganisms and other life forms, and tinting the water via exudation of tannins and humic substances. As you might guess, I encourage the fallen leaves to accumulate and decompose in the aquarium! 

Yes, I'll point it out again, because I keep hearing this myth: I don't talk about utilizing mangroves as a "nutrient export" mechanism in your aquarium because it would take many mangroves (like, more than your tank could ever accommodate) over many years to provide any noticeable nutrient export effect on your tank. Rather, we choose to focus on their unique aesthetics and their ability to foster the growth of other, beneficial life forms.

Sure, we could probably go on and on about keeping mangroves in your aquarium (and probably will again I the future), but I hope that this admittedly superficial review will encourage you to research more about these remarkable trees- and try them in your aquarium. 

In summary, a newer, more evolved interpretation of brackish water aquariums is both fascinating and necessary to push this interesting hobby speciality forward, IMHO.

Traditionally, in the aquarium hobby, when you've mentioned that you're 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 aquariums are 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.

Time to change that. Time to push forward...

I'd like to think that our small efforts at sharing a different approach to brackish water aquariums has been inspirational and informative. Of course, I have no illusions about this being "the best way" to do brackish. This approach is a bit more challenging, demanding, and dynamic than those we have taken historically when working in this niche. However, I think that this more evolved, functionally-aesthetic approach is a better way for those who are up for the challenge and hungry to try something new.

So, as we say "sayonara" to our current brackish tank, we say hello to a potentially new and very exciting era in the history of this hobby specialty area.

Stay excited. Stay inspired. Stay experimental. Stay diligent. Stay bold...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


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