Mixing, enriching...and learning...The dynamics of the botanical substrate...

One of the things I've always been a fan of in my aquarium keeping work is to allow nature to take its course in some things. I have this "thing" about not wanting to mess with stuff once it's up and running smoothly. Like, I will engage in regular maintenance (ie; water exchanges, etc.), but I avoid any heavy "tweaks" as a matter of practice.

In particular, I tend not to disturb the substrate in my aquariums. I think that it's because I imagine the substrate as this magical place which fuels all sorts of processes within our aquariums, and that nature tends to it in the most effective and judicious manner.

We talk about the concept of "substrate enhancement" or "enrichment" a lot in the context of botanicals (we tend to use the two terms interchangeably). We're not talking about "enrichment" in the same context as say, planted aquarium people, with materials put into the substrate specifically for the benefit of plants.

Rather, "enrichment" in our context refers to the addition of botanical materials for creating a more natural-appearing, natural-functioning substrate- one which provides a haven for microbial life, as well as for small crustaceans, biofilms, and even algae, to serve as a foraging area for our fishes and invertebrates. There is something oddly compelling to me when I look at both aquariums and natural biotopes with a diverse, interesting bottom structure.

I'm fascinated by alternative substrates in our aquariums.  Not just for plants, mind you, but for creating more realistic representations of what we find in nature...We've talked a lot about the composition of substrates within the waters of the natural habitats we love so much. And I keep coming back to it. I played around with this idea a lot in my brackish water aquarium, and it's fascinating...and fun!

It's funny, the planted aquarium world has made enormous strides in areas like lighting, fertilization, development of nutritive soils, and tissue culture of plants, but it seems to me that everything is geared around aggressively planted tanks, as opposed to stuff for the overall aquatic environment. I think this is an area where we as botanical-style aquarists can borrow from and contribute to with our work.

What has been lacking, IMHO, is development by manufactures of substrates based on the the materials found  in wild niche habitat, like flooded forests, seasonal streams, rivers, etc.- where so many of our fishes actually come from.  I think it's an area where we as hobbyists can make some real strides! 

If you've seen pictures and videos taken underwater in tropical streams (again, I'm pulling heavily from the Amazonian region), you'll note that there is a lot of loose, soil-like material over a harder mud/sand substrate. Obviously, using an entirely mud-based substrate in an aquarium, although technically possible- will result in a yucky mess whenever you disturb the material during routine maintenance and other tasks. You can, however, mix in some other materials with the more commonly found aquarium sands.

They are diverse harbors of life, ranging from fungal and biofilm mats, to algae, to epiphytic plants. Decomposing leaves, seed pods, and tree branches compose the substrate for a complex web of life which helps the fishes we're so fascinated by flourish. And, if you look at them objectively and carefully, they are beautiful.

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.

Would the use of terrestrial planting mixes and vivarium-style substrates be a more realistic representation of the types of substrates encountered in many of the ecosystems we attempt to replicate in our aquaria?

I think so! 

Remember, in general, blackwaters originate from sandy soils. High concentrations of humic acids in the water are thought to occur in drainages with what scientists classify as "podzol" sandy soils. "Podzol" is a soil classification which describes  an infertile acidic soil having an "ashlike" subsurface layer from which minerals have been leached.

That last part is interesting, and helps explain in part the absence of minerals in blackwater. And more than one hobbyist I know has played with the concept of "dirted" planted tanks, using terrestrial soils...hmmm.

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 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.

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.

Of course, there is always the potential danger of 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? 

Yet, I have this irresistible curiosity about the potential 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.

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.

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. 

And with 2019 as the "Year of the Planted Blackwater Aquarium" (it IS- I checked 😜), I think it's more appropriate than ever to explore these "crossover" concepts and see where they take us!

Brown, green...and pretty damn exciting! 2019 looks to be an interesting year!

Stay innovative. Stay curious. Stay experimental. Stay busy. Stay bold...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


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