Dirty thoughts from a botanical aquarium madman? Or, another concept to explore?

We seem to spend an inordinate amount of time talking about substrates and their appearance, functionality, and composition, don't we?

Yeah, I think we do. But hey...this stuff is really cool! And outside of planted aquarium, not too much thought seems to be given to the substrates in nature and in our aquariums...

"Dirted" or soil-based aquarium substrates are to me, about as interesting as it gets. A soil substrate essentially consists of mineral particles, organic matter, precipitated inorganic matter and microorganisms. Pretty natural. Hardly glamorous. However, they work really well to grow aquatic plants..


Of course, the problem with me is that I have a very marginal interest in aquatic plants, and an above average interest in how the substrates function within the overall aquatic environment, with an emphasis on the fishes...and 99.999% of all hobbyists that mess around with "dirt" in their aquarium are all about growing plants. Me, personally? Well, again- I'm more interested in creating a substrate that is essentially similar to the flooded forest floors of the Amazonian igapo, simply because it's what the fishes which inhabit these waters are used to. Plants? They're cool, but not my main interest! I'm a "dirted aquarium deviant.."

So, now that I've just angered and alienated about 80% of you, let me explain my thinking a bit more. 

As we've discussed before, the igapo are seasonally inundated forests. These forests have sandy, rather acidic soils with a very low nutrient content. The rainwater combines with the humic substances and tannins contained in the soils and the forest floor materials that are found on them. The acidity from the water corresponds to the acidic soils of these forests. They are the more nutrient poor than a comparable várzea forest, carrying less inorganic elements, yet higher concentrations of dissolved organics, like humic and fulvic acids. 

Amazonian várzea forests are flooded by nutrient rich, high sediments, and thus are very productive environments- some of the most productive in Amazonia. They are flooded by whitewater rivers, which inundate fertile alluvial soils within várzea forests, which helps explain some of the higher nutrient concentrations found in these waters, as opposed to the nutrient-poor blackwater which inundates and characterizes the igapó areas.

So I'm thinking that the more "classic dirted substrate" would be somewhat more reminsicent of the inundated várzea forests, although, with a few changes to the recipe, you could easily represent the igapo as well.

So, playing with this concept is pretty straightforward, in my experience.

Yeah, you start with organic potting soil, free from any fertilizers or other additives. I know others who have plaid with mixes that are something like loam, peat, and some fine sand. I think you can experiment with some variations on the formula, of course.

When you prepare this stuff for aquarium use, it's hardly a high-tech affair. You need to get it wet; saturated, but not liquid. Just sort of a gooey mud. This makes sure that a lot of the trapped air is gone...

A lot of hobbyists mix in some iron-based clays...like "potter's clay", for example. Again, consistent with the várzea soils and their alluvial basis, right? Some planted people will add some crushed coral or other calcium-based product (hey, maybe super-fine aragonitic sand?) into the mix for some KH support for plants. 

Typically, planted people will put down a layer that's about 1.5-2 inches (3.81-5.08 cm), and then cover the whole affair with a few millimeters of fine sand (like swimming pool filter sand)...I personally would use an inch or to of sand, but that's me. And that's it.

Then, the planted guys plant the hell out of it.

Which I wouldn't do. Not in my experimental fantasy world...

So, then I'd have this insanely nutrient-rich substrate, covered in a few inches of sand, and then I'd throw on all sorts of leaves and stuff on top of it.

Algae farm? Hydrogen sulfide bomb? Cloudy, stinky mess? A natural-looking and functioning substrate?

Possibly all of the above. And, what the hell happens to all of the susbtances released by this material if we're not trying to grow plants? This could be really problematic...Or not. But hey, it's an experiment, right? 

What if you boil and soak the soil for a week or so before you use it? Would that eliminate some of the "nutrient" materials contained within it? Hmm..Could you then end up with something that is a lot less "nutritious", but texturally and aesthetically and still sort of functionally similar to the natural substrates we're talking about? And couldn't you just mix the sand all around it, rather than put it on top to hold it down? And then you could mix stuff like leaves, Coco Curls, "Fundo Tropical", and other botanicals on top?

I mean, again- this could be a colossal mess...a stinking, cloudy pit. Or, it could be something that is aesthetically, and maybe functionally similar to the natural substrate found in these habitats?

Do you realize that I actually wake up in the middle of the night scheming about stuff like this? I mean, stuff that can result in complete disaster? Reckless, bordering on stupid? Well, I wouldn't go that far...But- perhaps stuff that takes a lot of unnecessary steps in multiple, seemingly undisciplined, and possibly opposing directions? Just..because.

Yeah, I do. Maybe you do, too? Some of you?

That's how you have to think, though, when you're pushing it. I think someone with a planted aquarium background, and perhaps a killifish interest (ya' know, 'cause killie hobbyists like to play with peat moss), and a passion for doing things exactly the opposite of the way your "supposed to" do them.

A rebel that plays with...dirt.

Where are you? Don't you want to mess around with this idea, too?

Go for it. Refine it. Beat the shit out of it. Work it. Develop it.

Create a breakthrough. Substrate that provides fishes with essential trace elements and other characteristics which could benefit their health would be really cool. Notice I said a focus on fish and not plants (ADA Amazonia and the like are for that!)Some people have done this before (Hello Leng Sy and "Miracle Mud"), and I think they've been on to something. We just need to give it a fresh look and refine some of my crude ideas here.

Why not use substrate enhancement to  influence/compliment/complete/enahnce the aquatic environment for fishes? It's what happens in nature...

"DIrt: It's not just for aquarium plants anymore." 

You've got this.

Okay, back to Saturday morning.

Be brave. Push the boundries. Aggravate others. Disrupt the boring routines.

Stay quirky. Stay fascinated. Stay obnoxiously undeterred by the criticisms of others...(But always listen to what they have to say, and consider it)..

Oh- and Stay Wet.

Scott Fellman

Tannin Aquatics



Scott Fellman
Scott Fellman


5 Responses

Mardhi Hamid
Mardhi Hamid

October 22, 2017

If the concern is having anaerobic conditions deep down in the substrate, why not setup a plenum? That will create anoxic conditions (oxygen levels 0.5 to 2 PPM) where specific bacteria strains reduces nitrate (and phospate) into nitrogen gas (through facultative anaerobic respiration).

further explanations:

Scott Fellman
Scott Fellman

February 19, 2017

Bruce- great ideas and information…the idea of producing a sort of compost is really intruiging I think there is much to learn from this process! Steve, good questions…I would likely avoid disturbing the dirted layer, for fear of releasing a cloud of “stuff” into the water column..I sort of envision my “dirted” system being composed of a higher percentage of sand, perhaps making some stirring of the substrate a bit more tolerable. I think there is a ratio" of dirt to sand that would work…I do agree to be conservative, especially with the Discus. Of course, an outsider to our litter world of tinting and botanicals would ask, “Why do this if you don’t grow plants?” LOL Alex, really like the idea of doing the decomposing substrate within the sand…Again, I think the idea is to see the impact of all of this influx of material on the overall environment. It’s very cool stuff!

Bruce F
Bruce F

February 19, 2017

I’ve always found the simplest way wet a dirted substrate is to fill the aquarium just to the level of the dirt and leave it that way for a day. Often you find you need more water as it is absorbed by the substrate. Most potting soils are full of junk you don’t need. I’d prefer top soil or dirt from the yard. Peat will help acidify. Over time as biofilms form these substrates tend to become more stable.
If you take clean leaves in the fall and soak them for a few days until they sink you don’t really need any dirt. By the following year you will have a substrate of the broken down leaves.
All these things depend on o2 moving through the system. You need to avoid stagnant conditions. Then everything is fine. You can smell when things go wrong and when you do you need to take action.

Steve Lancashire
Steve Lancashire

February 19, 2017

I like the thought process of these suggestions, and admire the bravery to try something like this out. My question would be how do I siphon out the fish waste to stop the No3 going through the roof. Also with keeping Discus if it all goes pear shaped it could be a costly error with Discus costing as much as they do.

That said, I keep Wild Discus and I am slowly coming round to the way of changing the habitat to a more natural environment and moving away from the planted tank.



Alex Cox
Alex Cox

February 18, 2017

That is an interesting idea and similar to something I am playing with now. I am mixing several substrates (sand and aquasoil) with the crushed leaf litter packs. That way some of the leaf litter will decompose into the subtrate. I am going to seed this with some soil (really muck and God knows what else) from my pond. Try to see what little critters I can get established in there.

If parameters check out I will attempt it on a larger scale with fish.

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