Approaching brackish with a different mindset...

As if you don't know by now, I'm pretty thrilled to be setting up some new tanks in my home office; among them, my "V 2.0" brackish water mangrove aquarium. The stated "mission" of this tank is to encourage my fellow hobbyists to give brackish a go..err, our concept of brackish a go, that is! Yet, despite our more "dirty" interpretation of brackish, I think it's a more accessible, purposeful, "honest" version than what is typically executed.


I say "honest" because we're not trying to take a "pure freshwater" mindset into this. We're trying to create a brackish water ecosystem.  It's different and I think it will make this a much more enjoyable and exciting way to execute it. Because it won't "force fit" fishes or ideas into the approach. It's not being set up to try to "wing it" with table salt, a few stones, etc. Rather, it's embracing the functional aspects of the brackish water habitat, focusing on the ecology first. The aesthetics will follow.

It's time to "big up" the "Estuary" concept!

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.

Function. Yeah. That's something we've long been obsessed with around here.

My obsession led me to launch Estuary by Tannin Aquatics in 2016- a line within the Tannin brand dedicated to the art and science of brackish water aquariums. When we launched this line, I knew full well that there would be like 27 hobbyists in the world who would have shown even a whiff of interest in the topic, and that was just part of the challenge. I realized that, much like when we launched Tannin and attacked blackwater aquariums with a different mindset and approach, it would take tiem to catch on.

And I'm pleased to see that it IS catching on! Slowly, but surely.

Now, first off, the hardest thing we've had to do- and continue to do- is to change the perception among hobbyists that brackish water biotopes are stark white sandy places with a few rocks. Noooooo! Actually, many brackish water estuaries and lagoons are way different than we've portrayed them in our aquariums over the years;

They are often turbid, brown-tinted waters, with muddy, rich bottoms covered with decomposing leaves, lots of micro and macro algae, some plants, and often dominated by palms and  mangroves. 

And I've heard the "warnings" from people about attempting to replicate this 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!"


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

And, unlike many of the prognosticators who predict doom and gloom, and who insist this can't work, or that the functional aspects of the habitats we're obsessed with can't be recreated in aquariums, I believe that they are perfect for replication. And yeah, I've actually been to quite a few of these habitats myself- dip net, refractometer, and ORP tester in hand- and I have the cuts, bruises, and insect bites to prove it! I've gotten up close and personal with mangroves, mud, and many of the wonderful organisms which call the "Mangal" home.

Trust me, these are way, WAY different than how we have traditionally portrayed brackish-water habitats in the aquarium.  There is a very serious disconnect that has always left me scratching my head.

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" freshwater plants...and it's been mired in that aesthetic hell for decades.

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- then on to the fishes. The wrong fishes, IMHO. Yeah-  big ol' puffers and Scats and Monos and Eels. Fishes that, although interesting, require large aquariums to keep successfully for any length of time. The size of the "preferred" fishes alone has, I'll bet, kept many hobbyists from venturing into brackish.  

I personally believe that not many hobbyists really want to dedicate a 200 gallon tank to some big grey, messy fishes, a few rocks, and some struggling freshwater plants- or worse. However, I'll bet that a lot of hobbyists might just want to dedicate a 15-40 gallon aquarium to smaller, interesting brackish water fishes, and some healthy mangroves...

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! 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.

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

Witness the rise of  a more natural approach: The botanical-method brackish-water aquarium.

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, filled with mangrove leaves, and perhaps stained a bit from tannins from fallen mangrove leaves.

Beautiful in a very different, yet oddly compelling way.

How does this all work? Ridiculously easy, really. The toughest part, as usual, is making the mental shifts to accept a different approach.

It all starts with my approach to substrate, and the mangroves which grow in it.

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, perhaps 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. 

Let's talk about plants for just a second...

This is another little rant that will likely alienate me from pretty much every YouTube aquarium channel and hobby forum out there. But really, sometimes there are things that simply have to be said, and since I don't really care if I take some heat, let me say it.

Why are we sooo insistent on keeping freshwater aquatic plants in our brackish water aquariums? 

Seriously, one of the top questions that I see on like every brackish water forum, Facebook group, or YouTube video is, "What kinds of aquarium plants can I keep in brackish water?"

I hate that question.


Well, because...It belies a fundamental unwillingness of us as hobbyists to let go of what we know and to embrace something different.  I mean, you're obviously new to the brackish world, so why try to bring along your old baggage with you?

Just enjoy the difference!

Sure, you hear a lot that Amazon Swords, Anubias, Java Fern, and other "hardy" plants may hang on in very slightly brackish water (like, up to say 1.003 SG max) situations. They may or may not do okay long term. And yeah, the elusive (and HUGE!) Crpytocoryne ciliata is known to actually be found in areas where there may be a very low salt content...But I think I've seen one...ONE brackish water aquarium with Cryptocoryne ciliatia in it. In the past 10 years.

Why do this? Why "force fit" freshwater plants into our brackish water aquariums?

This is that whole, "Well, the (fish/plant) can adapt to (insert your desired water parameters here) conditions, so, why can't I keep it in there....?" Argument.

It's dumb. I mean, sure- the plant can adapt...You can adapt to living in a 3 meter cube at 105 degrees F/40.55 degrees C  for the rest of your life, too...but would you want to? Would you be at your best? How do you think that would work out, long term?

Want my advice? (probably NOT at this point, I know...)

Just give up the idea of keeping freshwater plants in your brackish water aquarium. Ditch the idiotic "YouTube take" to brackish, and tell the next "content producer" who "recommends" that "approach" to shove it.

Seriously. Approach this differently.

All you are doing is trying to force freshwater plants which have developed a reputation for being "hardy" to adapt to an environment which is utterly alien for them. Sure, they may survive...for some period of time. But they're usually not thriving. Of course, you'll send me a video of your tank, which has a SG of 1.005 and has an obscene number of healthy Amazon Swords and Anubias thriving, as they have  for the last five years- but I assure you that you're the exception, rather than the rule. You couldn't seriously recommend keeping them this way to someone else...or could you? 

Really, have you ever seen a public aquarium representation of a brackish water habitat which contained Anubias, Swords, etc.? Probably not. If you have seen plants in these displays, they are likely riparian grasses which are salt and emergent growth tolerant. Usually, if there are any plants at all- they're mangroves. Or even just mangrove roots...

And before you bring it up- Seagrasses and marine macro algae can't typically survive for any length of time under less than natural seawater conditions, so instead, you'll need to find species of plants which are found in intertidal zones, like mud flats and estuaries, which have brackish water. There out there, but pretty hard to find in the trade....

So yeah, lose the whole "I want to keep aquatic plants in my brackish water aquarium" thing...

Like, honestly...Where in Nature have you seen a documented wild population of Amazon Sword Plants growing in a brackish-water habitat? You haven't, I'll wager.  

So, why bother?

And the really funny thing to me is that, when I search these YouTube videos where some content producer is sharing his/her brackish water aquarium, it almost always features one or more of these varieties of plants (most specimens of which appear to be in average health at best) and, in the ultimate ironic twist, they're being kept in tanks with fishes like Scats, which are known to tear up plants. Sometimes it's puffers, which is equally funny to me.

Like, why? Why?

If you are going to try something different, approach it differently...Make the effort to understand what's found in these habitats in Nature. Think about how you can replicate the function...

OMG, can we just agree as a hobby to "stand down" from producing any more of the mostly pathetic, absurd representations of brackish water "habitats" which are just all over the internet? 


Educate yourself by researching...not by watching some awful "amateur-hour "interpretation of brackish! 

Take a few minutes and look at some real brackish water habitats- what they really look like, and what is actually found in them-how they function, and why... and stop using those lousy YouTube versions of somebody's watered-down, zquairum-santized interpretation of what you're "supposed to have" in a brackish water aquarium as your model!

Read. Research outside of the aquarium world. You can do this. 

Yeah, take your inspiration from Nature!

And, why not take some time to learn about mangroves?


There are more that 50 species of mangroves found throughout the world. Mangroves thrive in oxygen-deprived sediments which would certainly spell doom for most plants. They have evolved certain morphological and physiological responses, which allow them to survive in these harsh conditions. 

Mangroves employ a sort of "internal ionic regulation." The Red Mangrove, Rhizophora mangle,  (the most common one we encounter in the aquarium hobby) is known to botanists as a "salt excluder", which separates freshwater at the root surface by creating a type of non-metabolic "filtration system."

The process of transpiration (exhalation of water vapor) at the leaf surface creates negative pressure in the xylem (the vascular tissue in plants that conducts water and dissolved nutrients upward from the root ). This causes a type of "reverse osmosis" to occur at the root surface. The salt concentration of xylem sap in the Red Mangrove has been found to be about 1/70th of the salinity of surrounding seawater, but this is l0 times higherthan in normal plants!

The Red Mangrove stores and disposes of excess salt in the leaves and fruit. (Which is one reason why we spray the leaves down regularly, which helps avoid salt buildup on their surfaces).

Yeah, mangroves are incredibly adaptable.

I've kept them for decades in all sorts of aquariums: Reefs, brackish, freshwater, and oh, yeah, blackwater.

The predominant species found in freshwater habitats is Barringtonia acutangula. It's definitely one you will notlikely see in the aquarium hobby. You might not know that mangroves do not require saltwater to survive. In fact, most mangroves are capable of growing in freshwater habitats, although most do not in the wild because of competition from other plants. However, some species DO need salt to grow and complete their life cycle.

Here are mangroves growing in a soft, acidic "blackwater" situation in Southeast Asia!

Mangroves are "halophytes" (salt tolerant plants), which maintain sufficient fresh water inside their cells and tissues to maintain metabolic function against a higher osmotic pressure in the exterior root environment, which can vary between freshwater and up to three times seawater salt concentration!

Mangroves have evolved some remarkable survival techniques, including a specialized reproductive strategy, in which seeds don't go through a "dormant" phase, and are viviparous, germinating while still attached to the parent plant. These seedlings (known as "propagules") are buoyant, photosynthetically capable, and are often transported in tidal and ocean currents, sometimes over significant distances.

Mangrove trees are able to withstand remarkable tidal changes, from partially submerged to completely exposed, then back to partially submerged again, all in the course of a day!

Mangroves are part of a highly diverse ecosystem. The productivity of mangrove habitats is important for supporting food webs. The productivity of mangrove forests can be equivalent to the most productive terrestrial forests! 

Mangroves are perfectly suited for their role as producers, and host enormous amounts of life within and among their structure. Because mangrove forests (sometimes called "mangals") are typically mud or peat-based systems, prop roots provide the hard substrate essential for settlement by many sessile organisms. This is also evident in the aquarium.

Let's talk about some practical aspects of keeping mangroves in your brackish-water aquarium.

First off, have some realistic expectations. They grow really slowly. My 18"-24" seedlings are over three years old. When you grow them from propagules, as I did, it takes time. You have to be patient. 

And the other important thing with mangroves in captivity is to not "mess with them" too much. Like, if you plan on keeping them in full-strength Marien water as seedlings, sprout your propagules in full-strength marine water. Brackish, sprout 'em in brackish...etc. Yeah, they're found in intertidal locales, subject to changes in salinity in the course of a single day...but that's in the wild. Of course, they can tolerate changes in salinity in captive propagation, if done slowly, but you don't want to make this a regular thing.

Unlike typical "aquairum plants" mangroves are not "window dressing", IMHO. They are the literal "stars of the show", and should be the life form that you're building your tank around. Makes the effort to meet their needs, and the entire aquarium and all of its inhabitants-will be better off for it- trust me. 

Oh, and far be it from me NOT to scold myself when it's deserved.

One thing I've done with this new version of my mangrove tank is to over-do it with the mangroves. I have way too many in there to create a sustainable very long-term situation. I have 7 seedlings in this small tank, a good chunk of my mangrove collection- all of which I grew from propagules legally collected in Florida.

They're almost sentimental to me, lol. I'm ridiculously attached to them. 


My mistake, though, was keeping these mangroves together in small containers for too long as they began to establish their buttress roots, and not pruning them as extensively or frequently as I should have. They became quite tall and leafy with relatively small root systems...something that would come back to haunt me later. As a result of keeping them like a "bouquet", their roots ultimately became an intertwined mess which took some very careful "surgery" to disentangle prior to planting them with proper separation in the new tank.

Now, here's the deal: Mangroves are TREES. They can become enormous in the wild. Want being said, this is a small aquarium in suburban Los Angeles, NOT a mangal in Southeast Asia. Mangroves grow quite slowly. Like, really slowly. And you can manage their growth by frequent pruning...almost sort of "bansai-ing" them.

Now, I"m not super in love with this practice, sustainable though it may be, but it's the best way to manage them long term if you don't have tropical estuary acreage upon which to grow your own mangal! Many hobbyists- myself included, have employed this practice to keep mangroves in modest setups for many years. And let's be honest, having a few sets of those cool prop roots in my tank is a great look.

And just having one small mangrove isn't gonna cut it, IMHO. These guys are 3 years old...To get a substantial root system enough to fill even this modest aquarium could take 3-4 more years. I'm patient, but that's too much even for me!

So, yeah, I have more mangroves in my little tank than I'd recommend. And they are a bit pissed off at me for disturbing them for the third time in a year and a half. So, a word of advice: Once you get your mangroves set, try to disturb them as little as possible. 

That being said, if managed in the way I just described, it can work. It's just not something that I'm particularly proud of, lol. Of course, I'm way prouder of employing too many mangroves than I would be trying to force-fit Anubias, Amazon Swords, or other freshwater plants into this display.

Okay, I could go on and on and on, but what about some smaller fishes? 

Ohh, that's a fun one. In fact, sooo fun, that we'll cover it in a separate installment!  


Scott Fellman
Scott Fellman


2 Responses

Florian Preissler
Florian Preissler

April 16, 2023

Hi Scott, just read your inspiring post about brackish water aquariums. I am thinking about setting up a brackish tank myself. I always disliked these sterile, white and bland brackish water tanks that seemed to be the standard. Your thoughts about brackish water biotopes was a big joy to read, thank you for that!
I have a question regarding roots and wood in brackish water. I read several times that wood rots extremely fast in saltwater and brackish water. It was even reported that it smells foul like rotten eggs (Ammonia?) and that it pollutes the water.
I’m hesitant using wood for decoration in brackish water, but your experience suggest its not an issue.
Would be happy to hear your opinon on that!
And please, please, please, keep up your good work and this blog!


August 04, 2022

Any of clams and mollusk they sell marine aquarist. Sutible for brakish water

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