Moving forward boldly.

Deeper still, we move into the natural, botanical-style aquarium world, eschewing "trends" and forging the "best practices" and "state of the art" as we go...

So, I've been told by watchers of the aquarium world that botanical-style blackwater aquariums are the "hot trend" in the hobby, which makes me laugh to no end. And we've been given more than our fair share of credit for helping elevate this speciality...

However, as I've stated so many times-no one "invented" this approach.  Using botanicals to create natural, blackwater environments in aquariums has been something that many hobbyists have been dabbling with for decades; it's just been seen by the hobby as more of a "side show" than a legitimate "approach."

The difference is- those of us in the hobby who are crazy about this stuff have simply upped our game and played a few misconceptions, misunderstandings, and downright "myths..." And we're looking to Nature for answers, doing common-sense homework, and employing radical new techniques to achieve our goals, instead of simply listening that guy who put up a YouTube video of his "Amazon-themed tank" and therefore must be an expert...

I know, I hear the collective groans from some corners. 

Well, look- I'm not trying to tell you that every YouTuber is a shallow, attention-grabbing poser- I'm merely stating that if you want real information, sometimes, you have to go deeper and do some real research work that doesn't involve just clicking  "play" on a video. And we can't delude ourselves into thinking that just because we can create a "look" that we aren't necessarily recreating the environment.

We need to move beyond the "contest-scape-as-the-ultimate-representation-of-Nature" mindset that, IMHO, is plaguing the hobby in some respects at the moment.

There is something comforting about the knowledge that you must be doing something right, huh? Especially when you look at Nature and go beyond the superficial, and real benefits for your fishes follow. When you research and attempt to interpret some of the amazing information done in the thousands of research papers on these habitats and environments by scientists, there is much to learn and experiment with.

And yeah, it requires us to be a bit bold...take some some unusual experiments. 


Now, sure, there are no guarantees of any sort of "good result" by simply switching to more appropriate natural conditions for your fishes, but enough stories keep coming our way that I can't help but wonder...

Like, I keep hearing from fellow hobbyists-recent converts to our blackwater, botanical-style approach…and they will proudly relate to me the story that their Apistos, which have been hesitant to do much of anything, suddenly spawned a week after they started utilizing botanicals in their aquarium…

Or that "ugly grey Barb" which suddenly started to get really colorful not long after!

Stuff like that.

Now, sure- it can be a matter of fortunate timing, multiple other factors, or simple coincidence- but I hear these stories enough that I have to wonder...

I mean I probably DO sound like a bit goofy when I say this, but man, there really is "something in the water." I think that the humic substances, tannins, and other compounds which are imparted by leaves, seed pods, and wood, too- create environmental conditions that, while maybe not exactly what our fishes might encounter in say, the rain forests of Asia or the jungles of South America, are similar in some respects.

Remember, these environments are replete with botanical materials from the surrounding forests and soils- and all of these materials have some chemical impact on the water.

What specifically is it about the presence of soils, wood, leaves and other botanicals which seems to have some sort of beneficial impact on our fishes? Well, the humic substances (I know, as big a “catch all” term as “tannins”) are documented by science to play an important role in fish health- specifically, cellular repair, stress reduction, metabolism, and disease resistance. I mean, yeah- these are BIG important things for fish health, aren’t they?



These substances aren’t present in quantity in just “any old aquarium”, filled with gravel, plants, and a few rocks. The ones we’re referring about come from plant materials- in our case, soils, seed pods, leaves, bark, and other parts of the plants in a given habitat. This is really important. And we know for a fact that they are found in the stuff that us “Tinters” throw into our tanks.


Oh, let's touch on those soils and substrates for just a tiny bit. A little information from South America that may give you some food for thought:

If you research the types of aquatic systems that we love- flooded forests- there are two common types- varzea, which are more productive, and tend to have darker,  more nutrient-rich, more acidic soils, flooded by so-called "whitewater" rivers, and igapo, which tend to have lighter-colored, more sandy/claylike substrates, and are flooded by blackwater rivers. Both habitats feature substrates that are typically covered with leaves.

The substrates have a significant influence on the plant population which resides in these habitats.  Species richness and diversity is far greater in the varzea forests, with highly productive herbaceous plant communities (terrestrial, of course), as opposed to the igapo, which has about half of the richness, and accompanying leaf litter accumulation and other botanical materials. 

In our aquariums, this is important to consider, in terms of substrates that we choose to use to simulate these unique habitats, as well as the type and density of the botanicals that we use. Like, planted aquarium substrates, versus simple silica sand or other materials, utilized based on specific habitats we want replicate.

There is a lot of research out there on these habitats and others worldwide. We just have to be willing today a bit deeper than the hobby forum story about the guy who threw in a few twigs and leaves and claims, "Orinoco!" We will continue to summarize the materials we find from perusing the vast body of scientific papers out there on these subjects, but you can certainly go deeper on your own of you're willing to do some homework.

Yes, as you've likely surmised by now,  just throwing botanicals and leaves into your aquarium filled with tap water won’t give you an “Instant Amazon” effect. You’ll need to reduce the pH and carbonate hardness by utilizing proper water conditioning (ie; reverse osmosis/deionization). However, you will be able to impart some of the tannins, humic susbtances, and other compounds into the water to a positive effect, even if you don’t pre-condition your water via RO/DI.

As we’ve said repeatedly- adding botanicals to your hard tap water will NOT lower the carbonate hardness. It might knock down the pH by a very small number ( like maybe .1 or .2). What you will get is some tinted water. You’ll get an aesthetic for sure. However, it's important NOT to delude ourselves into thinking that just because your tank looks a certain way that it's a completely functional representation of the habitats we obsess over. This is where we separate the "You Tube" view of our speciality from a more serious approach.

I've said it before and I'll say it again: An investment in a reverse osmosis/dionization (RO/DI) unit is essential for the serious aquarist who has aspirations of creating a low ph, low carbonate hardness blackwater habitat in his/her tank. And NO, we don't sell RO/DI units, so it's not a sales pitch, lol.


And you will get some benefits of the humic substances. I’m not 100% certain why it is, but one of my scientist friends confirmed for me that humic substances, are found in all sorts of aquatic environments (ranging from soft, acidic water to full-strength seawater). Of course, it's not that easy. Which humic substances? What tannins? Like, that’s the $40,000,000 question, right?


I am not aware of any definitive study that examined what humic substances and which specific tannins are present in a given habitat somewhere out there in the tropical streams, rivers, and lakes of the world.

Could you imagine if we knew WHICH ones and in WHAT concentration are found in specific locales? It would only be a matter of time before we would know how to create synthetic formulations of location-specific “humic/tannin cocktails”, which, when added to pH/hardness-appropriate water, could, in theory, yield conditions extremely close to those you might encounter in nature.


Welcome to the aquarium hobby- "2075 edition", right? 

So for now, we will jus sort of have to guess…and take a more-or-less “shotgun approach”, and just add leaves and botanicals to our tanks in the hope that some of these beneficial substances will leach out into the water column over time while they’re submerged in your aquarium.


Hey, it’s not as sexy as the “Open-bottle-add-super-specialized-formulation-for-the- Upper-Rio-Negro", but it’s a start, right? I liken it to an artist, painting with a very broad stroke to cover a  lot of blank canvas. About the most realistic thing we can do is to perhaps utilize botanical materials from the geographic regions from which our fishes hail and maybe we'll "capture" a few of the many humic substances and botanicals present there.

It's as much an "art" as it is a "science"- and we're really just beginning to look at these habitats and our practices from this perspective...

Yeah, we’re artists.

There is so much we don’t know yet. Or, more specifically, so much we don’t know in the context of creating optimum representations of natural environments for keeping fishes. We need to tie a few loose ends together to get a really good read on this stuff…until we get to the "Dial-a-River-just-instill-a-few-drops-of-this- additive" approach.


And I'm not all that sad about it.

There is something so satisfying about playing with the natural materials, and letting them influence the water in some fashion- however random or un-scientific that may be- as they have done for eons. Using our experience, observation, and of course, our test kits, when applicable!

And always, our intuition and creativity.

Stay resourceful. Stay diligent. Stay curious. Stay bold. Stay creative...

And Stay Wet.


Scott Fellman

Tannin Aquatics


Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

July 03, 2019

Thanks for the kind words…I think that an RO/DI unit, although initially more expensive, is such a great investment over the long-term for a fish keeper that it is even more important (and about the same price) as getting that next aquarium. The benefits of high quality, consistent source water that is “malleable” are really hard to beat! RO/DI product water becomes the environmental “blank canvas” upon which to create optimum conditions for your fishes.

Hmm…might be coincidence about he dories, but ya’ never know, right? And the fact that they’re foraging on the biofilm is one of the strongest cases for running a botanical-style aquarium…but you knew that already! 😆

Best of luck!



July 02, 2019

Good article, as usual, Scott.You’re making me think harder about an RO/DI. I just have a 55gal with tetras and panda corys, lots of plants. (I love plants!) My water is on the alkaline side of 7, and moderately hard. I started some adding botanicals about 6 months ago, leaves and pods, building up to a light tint. I really just wanted to try out the look, like it alot, by the way. Might be coincidence, but since I started adding leaves and pods, my Pandas have had a few babies! I see them foraging on the biofilm on the leaves pretty often.

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