Beneath the substrate...another component of "functional diversity" for the botanical aquarium...

Yesterday afternoon, I was busy engaging in that most enjoyable seasonal activity- clearing out our little vegetable garden to get it ready for the upcoming season. There's something nice and a bit relaxing about working in your garden, isn't there? And I think it's the same feeling many of us get when playing with our aquariums. Something about the soil itself that does it for me...

We definitely look at our aquariums as "gardens" of sorts, right? And gardens contain more than we perceive on our initial view, right?

What caught my interest as I was turning over the soil and removing some of the roots and remains of last year's plants was the large number of worms and insects that "work the soil" over, keeping it aerated and rich. Of course, being a fish geek, I kept thinking that there was some analogy to what we see in aquatic substrates. But the reality hit me that we typically don't cultivate anything more than "beneficial bacteria" in our aquarium substrates.

And of course, I had to give it some more thought. In reef aquariums, we are really into things like various worms which inhabit sandbeds. They're seen as part of a vital ecosystem in the reef tank, helping to process excess food and nutrients, creating waste material which feeds the "next guys down" on the food chain, and generally keeping fine sand from compacting too much.

In the freshwater aquarium, we seldom hear or even discuss such life forms, let alone, culture any for our aquariums. And what's weird is that I can't really think of any reason why we wouldn't want to...I mean, they're not going to eat your fishes, uproot your plants, or out-compete your Loricariids, Corydoras, etc. for food down there.

Is this another one of those "because it's not done that way" kid of things; some practice or belief rooted in both "tradition" and a bit of fear over trying something new? Or concern that, because you acknowledge that there is  enough "food" down in the substrate to support life, that your tank is "improperly maintained?"


And, since we are seeing more and more "rich, botanical-influenced" substrates appearing in our aquariums, as in our friend JT martin's tank below, you'd think that this would be an appropriate time to experiment with some of these  creatures in our tanks. I can see a lot of benefit to having some organisms in our systems which can help process the decomposing materials from pods and leaves, very similar to what occurs in nature in leaf litter beds. And, one could imagine that, just like in nature- there is a significant benefit to having them in the system as a supplemental food source- again, just like in nature. 

I guess the difficult part would be to obtain some of the insects, crustaceans, and worms that inhabit aquatic substrates. A good starting point might be to start with some crustaceans such as the reasonably easy to obtain Gammarus. This is a genus with over 200 species, many of which are found in exclusively freshwater habitats, and are commonly available as "life food" cultures.

Here's where it gets kind of interesting. They tend to feed on and among "allochthonous organic matter" (i.e.; leaves, wood, and botanical items) in streams and rivers. Freshly fallen leaves and other plant detritus that enter the water are rapidly colonized by microorganisms and fungi, and the Gammarus act as  "shredders", which feed on the leaves and on detritus that has been previously colonized by fungi. And your fish will munch on the occasional careless Gammarus that slips through the leaf litter...Hello, food chain.

And since we're all about leaf litter and botanicals in our aquariums, and studying the natural processes which occur there, this might be as good time as any to take an even closer look at how wild leaf litter beds function in nature, and how we can at least superficially replicate the process that occur within them.

Other possibilities for our initial foray into the world of substrate-dwelling aquatic organisms could be the Tubifex worms, or the so-called "Black Worms" (Lumbriculus variegatus) which are common to the trade. 

These worms inhabit aquatic environments, such as pods, swamps, and streams, and spend most of their time sifting through substrate and  feeding on microorganisms and  and organic material. And of course, our topical fishes LOVE them! SO, would there not be some benefit to having them inhabit your enriched substrate, "doing there thing" and providing the occasional "snack" for lucky fishes? Yeah....

Our friend Mike Bognich is experimenting with just such a setup in on of his experimental leaf-litter- bottom aquariums! A very cool idea that will benefit from more and more forward-thinking hobbyists playing around with it! 

And of course, in the wild, there are many other creatures which grow in the substrate/leaf litter beds, many of which we've never experimented with, or wouldn't want to (like larval stages of flying insects, mosquito larvae, etc.).

And of course, some are readily available, but are typically not animals you'd keep in aquariums, like Daphnia. Hello, refugium! 

Obviously, we're just literally scratching the surface here...There re numerous possible candidates for "in-aquarium" substrate dwellers, which would work well, not attack fishes, and which could perform a variety of roles in our tanks. As more and more of us look to nature for inspiration about substrates and litter beds and such, more and more focus will be paid to this seemingly neglected corner of aquarium study- and it's about time!

We are definitely looking forward to seeing more and more of you examine the more functional aspects of botanical-style/blackwater aquariums, and making meaningful and fascinating contributions to the aquarium hobby that will benefit others. Letting go of old beliefs and "rules", in search of answers, and unlocking secrets. 

Good stuff.

Stay curious. Stay experimental. Stay brave.

And Stay Wet.


Scott Fellman

Tannin Aquaitcs

Scott Fellman
Scott Fellman


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