Why you should be playing with "alternative substrate materials" in your aquariums...

As followers of "The Tint" know, we've been on this heavy "alternative substrate" kick for about 4 years now, pushing out our ideas and creations, sharing the fruits of our research both practically, and by delving into scientific literature. And the result has been a steadily growing interest in creating and managing unique substrates within botanical method aquariums. 

But the roots of our obsession with substrates goes back even farther- like to the earliest days of our company. 

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"- soils characterized by a whitish-grey subsurface, bleached by organic acids- caught my attention early on, and it led to a lot of cool ideas here. 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.  

Think about what goes on in the benthic (bottom) regions in the natural habitats we love, and what benefits or support the materials which aggregate there provide for the organisms within the ecosystem.

Understand that the substrate is a dynamic, extremely important part of the aquarium, too. And what we construct our substrate with, and how we manage it, is of profound importance to our fishes!

Fostering fungal growth, as well as other microorganisms and small crustaceans, should be a huge component of the "why" we do this. These organisms, as we've discussed repeatedly, form a part of the "food chain" within our captive ecosystems, and offer huge benefits to the aquarium not only as potential supplemental nutrition for fishes, but as a means to process and export nutrients from within the botanical-method aquarium.

A combination of finely crushed leaves, bits of botanicals, small twigs, etc. can form the basis for a more "biologically active" and even productive substrate. As these materials break down, they are colonized by fungi and biofilms, and impart  tannins, lignin, and other sources of carbon into the water to fuel a variety of microbial growth.


And of course, larger crustaceans and even fishes will consume the organisms which live in this "matrix", as well as possibly consuming some of the detritus from the decomposing leaves themselves. This is precisely what happens in natural systems.

I'm fascinated by the different types of soils or substrate materials which occur in blackwater systems, and how they influence the aquatic environment. Keep in mind that many of the habitats we obsess over, like Amazonian "igapos" and "igarapes" are seasonally-inundated forest-floor features, so it goes without saying that the terrestrial soil composition and associated biomass have significant influence on the aquatic environments that emerge during the wet season.

Its a very different looking- and functioning- substrate, for sure. And it can absolutely be replicated successfully in the aquarium. Adding materials reminiscent of those found in the wild to augment- or completely replace- the more "traditional" sands and other substrates used in aquariums is an easy "mental shift" that we can make and act upon.  

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," replete with botanical materials, will become an integral part of the overall ecosystems that we create. Considering the substrate as both an aesthetic AND functional component- especially in "non-plant-focused" 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 botanical-method 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. 

In a strictly aesthetic sense, the bottom itself becomes a big part of the aesthetic focus of the aquarium as well, with the botanicals placed upon the substrate- or, in some cases, becoming the substrate. Okay, cool. What are some other materials you can play with to create these "alternative" substrates?

How about...twigs?

Twigs are really fascinating to me as a substrate, because not  only do they create an interesting-looking substrate, they provide unique functional benefits as well. They create "interstitial spaces" (defined as "spaces between objects") which create areas for various fauna (small crustaceans, worms, and aquatic insects), as well as a surface for biofilm, algae, and fungal attachment and growth. The matrix offer protection for these organisms to grow.

Of course, it also provides a foraging area for the fishes. A place where they, too can shelter when needed. A place for them to spawn on and in. 

And of course, the twigs will leach tannins and other compounds into the water, which can impact the aquatic environment chemically. And, because of their physical structure, a substrate consisting substantially of twigs can create spaces for leaves and other botanical materials to accumulate, as well as to sequester our friend, detritus- which, as we've discussed repeatedly- is a valuable secondary food source for many species of fishes.

And of course, a mixing of elements - sand, sediments, crushed botanicals, etc., is yet another approach that you can take to creating a very unique and highly functional substrate. Allowing natural processes of decomposition to take place in and on the substrate is considered "best practice" in this approach.

Why? Because if we try to remove the detritus or other "offensive" material from a substrate created for this purpose, we're effectively depriving "someone"- some beneficial organisms- of their food source. Thus, a slowdown- or even a complete breakdown- of the very processes we're trying to foster-occurs.


There is something incredibly beautiful and useful about utilizing these alternative materials in our substrates. They have created an incredible opportunity for us as hobbyists to forge new directions in the hobby. And as a brand, the idea has really pushed me to develop some "off-the-shelf" solutions for hobbyists to experiment with.


I envision that the future of mainstream aquarium practice may one day include creating such a substrate as simply part of what we do. . For botanical method aquariums, which tend to be less plant-focused, establishing the "ecosystem" is very important.

(The part where Scott bitches and "editorializes a bit...)

Now happily, there are a few manufacturers who are starting to release and talk about different types of substrates for use in aquariums other than planted systems. 

It's a good start, helping to fill the gap in what has been a neglected hobby product sector (as we've been pointing out for years here), but it once again has resulted in some of these companies touting aesthetics above all, which, in my opinion, is not just disappointing, but a huge fail for the hobby. It keeps happing like this...

Why companies which tout themselves as "unique" or "progressive" continue to fall back on the vapid, vacuous "aesthetics first" mindset when creating and discussing what could be game-changing products if they just tweaked both the product and the messaging just a bit is beyond me. With the resources some of them have, it makes no sense to me to keep doing this.

Why do they do this? 

I think they do it this way because it's "safe", "easy", and fast to market. When you don't have to educate people on anything more than color and texture choices, all it takes is some capital to acquire and package your product, do a few social media posts, and release it to the YouTube "influencer" crowd- and your an instant "player..."

Ouch. Unfair, perhaps? But entirely correct.

So, hit me up guys, if you need some "consultation", lol. I can get your straightened out... I know that you can do better!😎

Okay, off the well-worn soapbox for now. 

To summarize, I think one of the most "liberating" things we've seen in the botanical-method aquarium niche is our practice of utilizing the substrate itself to become a feature in our aquariums, as well as a functional mechanism for the inhabitants.

In other words, if we do go down the road of looking at things in a strictly aesthetic sense, the bottom itself becomes a big part of the focus of the aquarium, with the botanicals placed upon the substrate- or, in some cases, becoming the substrate! These materials form an attractive, texturally varied "micro-scape" of their own, creating color, interest, and functions that we are just starting to appreciate.

In fact, I dare say that one of the next "frontiers" in our niche would be an aquarium which is just substrate materials, with minimal, if any, "vertical relief" provide by wood or rocks.

I've been beating that drum for a while now, huh?

I've executed quite a few aquariums based on this idea (specifically, with leaves), and I've been extremely happy with their long-term performance! Oh, and yeah-they kind of looked cool, too...

Nature provides no shortage of habitats with unusual substrate composition for inspiration. If we look at them in context of the surrounding terrestrial ecosystem, there are a lot of possible "functional takeaways" that we as hobbyists can apply to our aquarium work.

And the interesting thing about these features, from an aesthetic standpoint, is that they create an incredibly alluring look with a minimum of "design" required on the hobbyists' part. Remember, you can to put together a substrate with a perfect aesthetic mix of colors and textures, but that's about it.

We have to "cede" some of the "work" to Nature at that point!

Once your substrate is in place, Nature takes over and the materials develop that lovely "patina" of biofilms and microbial growth, and start breaking down. Some may be moved about by the grazing activities of resident fishes, or otherwise slowly redistributed around the aquarium. I suppose the degree to which this happens is dependent upon the type of substrate material you utilize.

This is not unlike what occurs in the wild habitats...newly inundated forest floors have a lot of leaf litter, seed pods, etc., and will be quite turbid for some time. If you understand the context for which they are intended, and the habitats which they help to replicate, this is perfectly acceptable and logical...Of course, you need to make that "mental shift", right?

Much like in Nature, the materials that we place on the bottom of the aquarium will become an active, integral part of the ecosystem. From a "functional" standpoint, bottoms comprised of substrates supplemented with a variety of botanical materials seem to form a sort of "in-tank refugium", which allows small aquatic crustaceans, fungi, and other microorganisms to multiply and provide supplemental food for the aquarium, as we've touched on before over the years here.

Let's keep on this stuff.

Let's keep questioning aquarium hobby dogma, but let's not become dogmatic ourselves. Let's call out shoddy work and b.s. when we see it, but not to the point of stifling anyone. Let the manufacturers know they should up their game (that includes me, too..)

And, if we're off on our assertions, let's figure out why, and see just what is actually happening in our tanks. If you haven't; figure this out by now, the whole world of botanical method aquariums is, in actuality, one big, grand experiment- and everyone is invited to play!

That means YOU!

Stay creative. Stay excited. Stay motivated. Stay curious. Stay unique. Stay observant. Stay diligent...

And Stay Wet.


Scott Fellman

Tannin Aquatics  


Scott Fellman
Scott Fellman


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