Sorting through substrate and pushing out of the comfort zone...

Have you noticed that some of the things that we do and materials that we utilize in our aquarium paractice have remained largely unchanged for many decades? I mean, we as a hobby tend to fall into the "comfort zone" afforded by stuff that gives the widest variety of aquarists the best possibilities for success and replication. 

It makes sense, of course, from both a hobby and a commercial standpoint. 

That being said, it's nice to experiment and push the outside of the envelope periodically with things that may not be 100% tried-and-true, right? 

One of the things I've had a fascination with in the aquarium hobby is the substrate materials that we've used on the bottoms of our aquariums. It's funny, but looking back on my hobby "career" (really, spanning virtually my entire lifetime), the choices we've had for many decades were surprisingly...well, dull. And actually, kind of "unrealistic", actually.

I mean, the old standby,"#3 Aquarium Gravel" is not exactly reminiscent of the materials found in most of the tropical aquatic environments of the world! Yet, over the decades, this ubiquitous material became THE standard for aquariums. Why? Well, "back in the day", the medium particle-sized gravel was anointed  "easy to maintain", as it tends not to accumulate a lot of uneaten food and organic debris. A siphon or "gravel vac" could easily penetrate the surface layer, picking up the debris while leaving the substrate itself essentially undisturbed. In addition, many of the gravel materials tend to have some buffering capacity, which is good for many fishes, specifically those like African cichlids, etc.

It's only been in recent decades where we've seen a wholesale "migration" to different materials. I see two primary reasons for this: The rise in popularity of planted aquariums, which necessitated the development of specialized substrates, and reef aquariums, which require specific types of aragonite sands for buffering and such.

Many of the newer commercial products are specifically formulated to provide minerals, trace elements, etc. for plant growth, lower pH, etc. That's really cool- what I call "smart substrates" are, I think, the wave of the future. And of course, we are fascinated by the people who play with so-called "dirted substrates" in their planted tanks... similar in many respects to the ideas we are intrigued with.

As we talk about so much here, what we call "functional aesthetics" is the name of the game here. And of course, these specialized substrates are fantastic and far more realistic, in my opinion, than gravel for a broader variety of habitats. You can create some really awesome looking (and functioning) substrates. 

And that's where we come in...

When we started Tannin, my fascination with the varied substrate materials of tropical ecosystems got me thinking about ways to more accurately replicate those found in flooded forests, streams, and diverse habitats like peat swamps, estuaries, creeks, even puddles- and other bodies of water, which tend to be influenced as much by the surrounding flora (mainly forests and jungles) as they are by geology.

Now, a unique class of substrate, the"Podzols" -are soils characterized by a whitish-grey subsurface, bleached by organic acids. They have an overlying dark accumulation of brown or black illuviated humus. These soils support the rainforests surrounding blackwater streams, yet are the most infertile soils in Amazonia. 


And of course, my obsession with botanical materials to influence and accent the aquarium habitat caused me to look at the use of certain materials for what I call "substrate enrichment" - adding materials reminiscent of those found in the wild to augment the more "traditional" sands and other substrates used in aquariums.  And in some instances, to replace them entirely.  

We have sourced materials which we feel recreate some of the appearance, texture, and function of the tropical streams and rivers that we obsess over. Some, like "Fundo Tropical" and "Substrato Fino" are coconut-derived, and will not only "tint" the water, but will impart those humic substances and such that seem to be so beneficial for many fishes. And then we have our more "leaf-centric" materials, such as Mixed Leaf Media and "MLM2", which provide a different look and function.

The texture of these materials tends to facilitate the growth of small life forms, like  bacteria and higher organisms (like worms, creatures like Gammarus, and other crustaceans) can thrive and reproduce, processing uneaten food and other materials, which providing the occasional "snack" for foraging fishes. 


I suppose the "cons" of incorporating these types of materials would be that you could overdo it. You know, adding too much too soon, possibly overwhelming the resident bacteria population in an established aquarium. Potentially rapidly reducing pH or even oxygen with excess enthusiasm! It's possible- perils that are well-known to most in our community. Working with ideas like this always requires that we proceed slowly and cautiously- looking at the potential for issues as thoughtfully as we do at the opportunity to do "evolutionary" things.

And then there is that curious, nagging "thing" I have in my head about the ability of botanical-influenced substrates to foster denitrification. With the diverse assemblage of microorganisms and a continuous food source of decomposing botanicals "in house", I can't help but think that such "living substrates" create a surprisingly diverse and utilitarian biological support system for our aquariums.

With our embrace of "detritus" or "mulm" as a source of "fuel" for creating active biological systems within the confines of our aquariums, I think that the idea of an "enriched substrate" will become an integral part of the overall ecosystems that we create. Considering the substrate as both an aesthetic AND functional component- even in "non-planted" aquariums, opens up a whole new area of aquarium "exploration."

I envision that the future of mainstream aquarium practice may include creating such a substrate as simply part of what we do. Adding a mix of botanical materials, live bacterial and small organism cultures, and even some "detritus" from healthy aquatic systems may become how we establish systems. For blackwater aquariums, which tend to be less plant-focused, establishing the "ecosystem" is very important.

And the idea is not THAT crazy- it's long been practice to add some sand or filter media from established aquariums into new tanks to help "jump-start" necessary biological processes.  It makes sense, and the overall concept is really not that difficult to grasp. And we probably shouldn't get too crazy into understanding every single aspect of this practice. Suffice it to say, something about this practice works, for reasons which we already tangentially understand. 

The biochemical interactions and such can and should be explored by those with the proper backgrounds, but for most of us, simply experimenting with and observing our aquariums and the way they operate can yield a surprisingly large amount of information. 

Interested? I sure am!

It's not some amazing "revolution"- it's simply an evolution of practices that we've been playing with peripherally for decades in the hobby. It's about experimentation and observation. It's a way of looking at what's already working and trying to figure out the "whys" as we go. 

Building a botanical-style aquarium system is not simply about a different look. It's about creating a biological system optimized for the blackwater environment. With a substrate comprised of botanical materials which specifically compliment the overall aquarium, the possibilities for success with these unique systems are significant!

We are committed to experimenting and learning more about the role of botanical substrates in our aquariums, and are really excited about the future!

Who's in?

Stay excited. Stay curious. Stay observant. Stay creative...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


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