Here's mud in your...tank? Question everything.

One of the things I like about the approach that we are taking to natural-style aquariums is a willingness to look at things a bit differently; to occasionally push the boundaries back on what is considered "normal" practice and the "tried and true." We've talked so often about the need to make "mental shifts" and turn towards Nature, rather than the traditional hobby practices, for a variety of things that we do. I think that this opens up more possibilities than ever before for those who are willing to do the work and venture out on the roads less travelled.

As you know, we talk a lot about substrates here- particularly in the context of their environmental impact on our aquariums. Not simply as an aesthetic enhancement to an aquarium, but as a crucial environmental enhancement component. The idea of re-imagining the materials, practices, and the ways we incorporate various materials into the substrates of our aquariums is prime for disruption (Okay, I had to use that expression!). Sure, at first glance, you might think to yourself, "Who cares? What's so incredible about substrates and why do we need to change anything?" 

Fair enough. For many years, they haven't really been considered much more than the metaphorical "window dressing" for our tanks. We've seen some evolution of them for aesthetics and for plants, but that's been about it. 

However, the reality is that aquarium substrates can have such an impact on our little ecosystems, beyond just creating a "look." Not surprisingly, we've seen a lot of developments in the area of planted aquarium substrates- creating nutritional media for aquatic plants to grow in and thrive. This has been a big thing for the hobby, of course. However, with few exceptions (I've seen "shrimp-centric" substrates) it's been focused solely the needs of plants- not the aquatic environment as a whole.

I think it's time to change that in a big way.

And it starts with re-thinking what we use. If we want to replicate the wild aquatic habitats of the world, we need to consider what they actually are.

It starts with finer, siltier, more "soil-like" substrates- Now, sure, there are many habitats which are comprised of fine sands, and even coarse gravels, as we've incorporated into our aquariums for a century now. However, many, many natural aquatic systems have substrates comprised of clay, minerals, silt, and soils- perhaps with a smattering of fine quartz or other sand. I'd go out on a limb to suggest that many, if not most- of the intriguing habitats we are interested in replicating in our natural aquariums have substrates unlike anything we typically utilize in the hobby.

For some time, I've been very intrigued about the terrestrial and other soils that hobbyists who keep "dirted" planted aquariums have utilized for years to facilitate amazing plant growth. However, I'm not talking about them for growing plants- I'm talking about using these materials for the primary substrate in the natural, botanical-focused aquarium, in which plants may or may not play a role. Now, sure, there are considerations- such as an influx of a lot of nutrient-laden materials into the aquarium (not as important if you're growing plants, of course), and the sheer "messiness" of soils, clays and silt-which have created some consternation among those who use them. Sure, these materials are easily disturbed and can create some rather turbid conditions in the tank as they settle. 

I've heard about concerns over gasses and such being trapped under the soil substrate (likely more of a concern when you're employing a "cap" of sand or other material on top of the soil/silt/clay to retain it) and being released into the tank during maintenance and other activities. Now, in my experiments, I have not experienced this. I don't use a "sand cap" on top of my "dirt"- rather, I tend to mix in bits of crushed leaves, botanicals, and twigs, which seems to not only keep the materials together, but enhances the natural, "random" look. I gradually saturate and "flood" these tanks, a sort of analog to what happens in Nature during the periods of inundation in the forests.

I'm sure that I'll get a dozen emails from hobbyists telling me that it's irresponsible snd dangerous to utilize such an approach to substrate in a fish-focused tank, but in almost 7 years of personal experimentation with these types of mixes, I've never had any issues whatsoever- other than the aforementioned cloudiness when the substrate is disturbed. In fact, after a few months, even when the substrate is disturbed in one of these tanks, the cloudiness tends to not occur. Based on my personal experience, I believe that the longer this stuff is down, the more likely it is to STAY down.

Now, does this mean everyone should ditch the time-proven commercial substrate materials and jump head long into creating dirt and silt substrates in their display aquairums?

Of course not.

However, I think it's worth experimenting with.

It's very important to look at our long-held opinions about what aquarium substrates "should" be, and what their role is in the aquarium. We've long offered a variety of materials which we've rather generically called "substrate additives"- stuff you can mix in with conventional sand, soils or use as a primary substrate in experimental systems. Many of you have used our coconut-based coir substrate material, "Fundo Tropical"  or the finer "Substrate Fino" for this purpose over the years as an alternative to peat and such, and it remains a best-seller for I think you're finding interesting uses for this stuff, too.

I think that we should look at substrates in our aquariums as more than just "the bottom" or "a place to put rocks and wood and plants"- but rather, as a dynamic, living, integral component of a balanced closed ecosystem. A place to culture supplemental food organisms, facilitate reproduction of fishes (I'm thinking soil-spawning killies here), and impact the chemical composition of our water. It would be great to apply as much emphasis to substrate in this vein as we do to other components of the aquarium. It's about mental shifts; re-thinking the "how's" and "why's" of what we've done for so long.

A "substrate" can be- should be- way more than gravel or plain old sand.

And if we have our say in the matter, it will be!

If one studies the composition of the substrates in the flooded forest habitats of South America that we obsess over, they are mainly comprised of clays, soil, and silt, with a whitish quartz sand in some more permanently inundated areas. The igapo tend to have a less diverse and species-rich plant/tree population because the soil which comprises this habitat, known as podzol- tends to be more depleted of nutrients than the more dense, productive varzea habitat, which has a far "richer" soil.

Taking the time to study these habitats in their "terrestrial" state and understanding the composition of the soil and plant species which reside in them can make a huge contribution to our knowledge as we attempt to replicate them in our aquariums. Yeah, if you would have told me twenty years ago that I'd be reading scientific papers about, well- dirt- on the forest floors of Amazonia, I would have been like, "Um, yeah...right..."

However, the reality is that in order to replicate these rich flooded forests as an aquatic habitat, we need to understand them in their terrestrial state as well. Our friends who keep frogs and other herbs have an interesting understanding of these habitats, and we would do ourselves some good reaching out and discussing this sort of stuff with them!

One of the characteristics of our beloved igapo and varzea environments (flooded forest floors in South America), and indeed, many of the other tropical stream habitats worldwide, is a large number of roots in the substrate. The igapo, in particular, has a large number of smaller roots, because of the relatively nutrient-poor soils. To simulate this in the aquarium, you could utilize a variety of dried roots, or even small pieces of wood, like "Spider Wood", "Tangle Branch Wood", or even our "Nano" Asian driftwood, Mangrove Branches, etc.

In Nature, these roots don't just serve to provide nutrients for plants- they also create a protection against erosion and loss of sediments. In our aquariums, we can utilize the aforementioned materials to hold some of these materials together. And, sure, if you're really cutting edge, you can experiment with water-resistant terrestrial plants, like sedges, grasses, etc., which lay down significant root systems in these substrates.

"Functional aesthetics", again.

Now, what about maintenance? What are the issues? Well, much like any aquarium with substrate, you need to be smart, observant, consistent, and in the case of soils and such- patience- as these systems establish. You will need to feed and stock carefully, and sure, unless you like haziness, you'd be well served not to excessively disturb the substrate too much, particularly during the earlier phases of the tanks existence.

There is so much more to research, experiment with, and discuss in this area. We'll have a lot more to say about this stuff in coming months. We're excited about the possibilities which are arising as a result of this work. The potential to replicate- on many levels- the look, function, and dynamics of the substrates found in Nature.

The potential opportunities and breakthroughs are there...We just have to dig in and go after them!

That's where Tannin is headed. We're doubling down in coming months, beyond anything we've done before- and likely, with unique natural materials beyond anything available anywhere previously. There's no turning back now....

And of course, the long-awaited "Nature Base" substrates will be available soon...Get ready for turbid tanks, dark water, biofilms, and all sorts of coolness! 

Stay engaged. Stay resourceful. Stay observant. Stay patient. Stay intrigued...

And Stay Wet.


Scott Fellman

Tannin Aquatics 



Scott Fellman
Scott Fellman


1 Response


December 08, 2021

This was very helpful such an amazing article and i totally agree we should use more soils in our fish tanks great idea.

Leave a comment