Bottoming out...Rising Up. Another look at he "substrate only" aquarium concept!

Let's get to the bottom of things...again.

Today, we dip into the Q &A for a great question and what I hope is an interesting and motivating discussion! 

Q- You place a lot of emphasis on the stuff on the bottom of the aquarium. How does this differ from "active substrates" for planted tanks, and are there other benefits for aquariums that you can gain by using botanicals as the substrate?- J.C., Rockford, IL (USA)

A- I love your question! I think one of the most "liberating" things we've seen in the blackwater, botanical-style aquarium niche is our practice of utilizing the bottom itself  to become a feature aesthetic point in our aquariums, as well as a functional mechanism for the inhabitants.

In other words, in a strictly aesthetic sense, the bottom itself becomes a big part of the aesthetic 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 "microscape" of their own, creating color and interest. In fact, I dare say that one of the next frontiers in our niche would be an aquarium which is just substrate materials, without any "vertical relief" provide by wood or rocks.

There are many examples of small pools and other aquatic features in nature to provide inspiration.

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 it's in place, nature takes over and the materials develop that lovely "patina" of biofilms and microbial growth, and start breaking down, are moved by fishes, or otherwise slowly redistributed around the aquarium.

A literal "active substrate", indeed! Yet, something that is fascinating and beautiful for those who give the idea a shot!

This is a big aesthetic shift in the hobby, but it goes beyond that.

I mean, sure, we've done hardscapes before, with wood and stones dominating the 'scape. However, our tanks have placed far more emphasis on the "functional" aspects of the botanical materials we use.

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 our supplemented with a variety of botanical materials 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.

They've become not only physical places for fishes to hide and forage among- they've become an integral part of the entire closed aquarium ecosystem itself, helping influence water parameters, foster growth of fungi and microorganisms, and just maybe- some form of nutrient export/denitrification (although that last part is still a bit speculative).

It's certainly no stretch to call our use of botanicals as a form of "active substrate", much like the use of clays, mineral additives, soils, etc. in planted aquariums. Although our emphasis is on creating specific water conditions, fostering the growth of microorganisms and fungi, as well as creating unique aesthetics, versus the "more traditional" substrate materials fostering conditions specifically for plant growth.

And, as we play more with botanicals, we're finding out more unique ways to work with interesting materials to create substrate-centric systems that check all the boxes: Functionality. Interest. Aesthetics. Stability.

We've talked about "functional aesthetics" created by botanicals in the aquarium, the potential for additional biological support/filtration (and potentially even denitrification), and it's a big, BIG topic, with lots more to be explored,  discovered and deployed in our aquarium...flirting with a "substrate-only" tank is one of those tantalizing, at first seemingly awkward, yet ultimately transformational little projects we can play with. 

Lots of cool things we can play with. Lots of cool experiments to do. Lately, I've been thinking of playing with our "Twenty Twigs" pack, mixed with a matrix of small leaves and botanicals, to be the entire scape in an aquarium. This could be interesting, I think!

Stuff like that truly pushes the boundaries between what we do al the time in the hobby, and those outer regions where few have tread before. There will be challenges, discoveries..and rewards for taking this road less travelled.

Who's in?

Stay excited! Stay unique. Stay adventurous. Stay creative. Stay undaunted...

And Stay Wet.


Scott Fellman

Tannin Aquatics 




Scott Fellman
Scott Fellman


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