Enriching substrates and embracing biodiversity- the aquarium world's next evolution?

One of the things I've always found amusing in the aquarium hobby is thinking about the types 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 of "#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.

And of course, there are sands, which 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 I think that in the past decade or so, we've seen an explosion of cool sands and other substrate materials. I think that the explosion of interest in planted aquariums fed this influx of exciting new substrate materials.

Adding fertilizers, various grades of substrate materials, and other additives is something that we see a lot in the planted are of the hobby. There's been some really great work in that area, and a lot of interesting developments in the planted aquarium world. 

I think that this same idea of creating "enriched substrates" is applicable to non-planted aquariums as well. I've played a lot with this in my brackish-water aquarium work of late, and it's validating many of the theories I've maintained for many years about substrates and their place in the overall aquarium environment.

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 others which tend to be influenced as much by the surrounding flora (mainly forests and jungles) as it is by geology.

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 generically call "substrate enrichment" - adding materials reminiscent of those found in the wild to augment the more "traditional" sands and other substrates used in aquariums to foster biodiversity and nutrient processing functions.

I think that these materials can really work well with sands and other more commonly used substrate materials. And in some instances, to replace them (almost) entirely- if not entriely!

Now, adding things like crumbled leaves, fine-particles coconut-derived materials, and such does have pros and cons. The benefits would be that you have "in situ" release of tannins and other compounds into the water column, a rich and diverse substrate in which 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" 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. Stuff that decomposes in our tanks is bioload, right? 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.

Be careful...

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. I've had some good discussions with my friend Nikolay Kraltchev about this, and he's thought about this from a planted tank perspective as well as an overall biological one. Other botanical-style aquarium enthusiasts have done remarkable things with this idea.

The implications for successful aquariums are manifold.

I mean, it's not THAT crazy- it's long been practice in freshwater and marine aquariums 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.

The biochemical interactions and such can and should be explored by those with the proper backgrounds, but for most of us, simply observing our aquariums and the way they operate can yield a surprisingly large amount of information. Something about this  practice works, for reasons which we already tangentially understand. However, there is lots more to learn.

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 a way of looking at what's already working and trying to figure out the "whys" as we go. 

In the mean time, I'm going to keep playing with different substrate materials, and mixing botanicals and such into my substrates. It's too irresistible for me not to do this!

I hope it's the same with YOU!


Stay progressive. Stay thoughtful. Stay curious. Stay experimental...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


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