Sands, soils, and supplements...a quick look at the world of "functionally aesthetic substrates..."

I admit...I'm not a horticulturist or aquatic plant specialist. I have a really great terrestrial garden at home, and I admire aquarium plants. So I suppose that may qualify me to talk about aquarium substrates today! 😂

(Worst "stretch" in history, for sure- even for me!)

Specifically, 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!

Now, like 90% of the aquarium world, I love many of the substrates offered by commercial manufacturers. I love them a lot. And trust me, if I wasn't hell-bent on my botanical-style aquarium segment, I'd be like 100% substrates. Nothing else. Seriously! Shipping would, of course, kill me, and it would be heavy, back-breaking work, and..

Okay, digressing. A lot. Back to the topic at hand.

SO, gravels and sands are cool; they form the backbone of the aquarium substrate category. There are so many coming out these days it's hard to keep track of. Specifically in the planted tank and shrimp arenas, substrates have been developed with specific needs in mind.

Cool stuff.

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! 

Consider natural waters and the impact of the substrate. In rivers, such as the Amazon, Rio Xingu, or Orinoco, you'll find materials that originate in the mountains and highlands, and gradually work their way downstream, influencing the aquatic environment chemically, physically, and geographically. 

The materials are influenced by the currents and water movement, tend to "sort themselves out", and re-organize over time. To simulate this dynamic, it pays to do a little research on the specific environment that you're looking to replicate. Some parts of the Amazon, for example, are replete with larger particles of material, with a covering of fine sand.

The first recorded observations of bed material of the Amazon River were made in 1843 by Lt William Lewis Herndon of the US Navy, when he travelled the river from its headwaters to its mouth, sounding its depths, and noting the nature  of particles caught in a heavy grease smeared to the bottom of his sounding weight. He reported the bed material of the river to be mostly sand and fine gravel. Oltman and Ames took samples at a few locations in 1963 and 1964, and reported the bed material at Óbidos, Brazil, to be fine sands, with median diameters ranging from 0.15 to 0.25 mm.

Interesting history..

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 sand.

That was the whole thinking behind "Substrato Fino" and "Fundo Tropical", and "Pedacos de Fruta", three of our most popular substrate "enrichment" materials. They are perfect for helping to more realistically replicate both the look and function of the substrates found in some of these natural habitats. 

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 encourage you to study the natural environment, particularly niche habitats or areas of the streams, rivers, and lakes- and draw inspiration from the functionality of these zones. The aesthetic component will come together virtually by itself. And accepting the varied, diverse, not-quite-so-pritinh look of the "real thing" will give you a greater appreciation for the wonders of nature, and unlock new creative possibilities.

In regards to the substrate materials themselves, I'm fascinated by the different types of soils or substrate materials which occur in blackwater systems and their clearwater counterparts, 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.


In general, blackwaters originate from sandy soils. High concentrations of humic acids in the water are thought to occur in drainages with what scientists call "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.

Also interesting to note is that fact that soluble humic acids are adsorbed by clay minerals in what are known as "oxisol" soils, resulting in clear waters."Oxisol" soils are often classified as "laterite" soils, which some who grow plants are familiar with, known for their richness in iron and aluminum oxides. I'm no chemist, or even a planted tank geek..but aren't those important elements for aquatic plants? 



We have the terrestrial environment influencing the aquatic environment, and fishes that live in the aquatic environment influencing the terrestrial environment! This is really complicated stuff- and interesting! And the idea that terrestrial environments and materials influence aquatic ones- and vice-versa- is compelling and could be an interesting area to contemplate for us hobbyists! 

It already is, to some extent, as the whole idea of utilizing botanicals (from terrestrial sources) in our aquariums encompasses these processes. 

It's fascinating to contemplate the things that happen where soil, water, and fishes meet...

Damn, this shit's cool!

Lots to learn. Lots to think about. A lot to experiment with! More to play with! 

Stay open minded. Stay curious. Stay creative. Stay engaged. Stay excited...

And Stay Wet. 


Scott Fellman

Tannin Aquatics


Scott Fellman
Scott Fellman


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