My "sphere of obsession..."

Have you ever had that one fish- or a bunch of fishes, which you "are gonna get to eventually?" You know, you're planning on setting up a tank for ___________?

Yeah, that's me.  I have a huge list of 'em.

And, with my long-time love affair with botanical-style aquariums, it's never been a better time for me to experiment with some of those more exotic fishes, most of which (surprise!) come from blackwater habitats in the wild. And most of these habitats are ideally suited to replicate in specialized aquariums.

Think of the breakthroughs we can make with some fishes in small, specialized tanks!

I have a crazy obsession with some of the unusual Anabantoids, like the "Licorice Gouramis", "Chocolate Gouramis", and such. You know, those little, somewhat shy, and rather specialized species that always seem to "do best in a dedicated setup"- six hobby "code words" for "you'll likely never keep them unless you have a 75-tank fish room."


Of particular interest to me of late has been the so-called Chocolate Gourami (Sphaerichthys osphromenoides). I love this species not only because of it's relatively small size- I love it because of it's subtle, "tan on brown" coloration, relatively passive demeanor, and their perfect appropriateness for a blackwater, botanical-style aquarium, replete with leaves, seed pods, and twigs.

This fish has a fairly wide range, but is well-known to come from Malaysian state of Sarawak and Indonesian province of West Kalimantan (Kalimantan Barat). They tend to be found in highly acidic, blackwater habitats, such as the endangered peat swamps and blackwater streams in rain forests. 

And it's tiny.

These little gouramis, although not known to be specifically "gregarious" in nature, are interesting when kept in groups, displaying unique behavior and color. Yet, they simply aren't community tank fishes. And they like relatively warm water, too! Like 75-82°F./24-28ºC- so you need to keep this in mind when equipping their tanks. 

On the other hand, the cool thing about some of the fishes in my "sphere of obsession" are generally small fishes. Like, usually surprisingly small. I have no idea why. Now, we already know I prefer smaller fishes, but it's kind of crazy how most of the fishes on my "wish list" are little guys. 

I think many come from specialized habitats. And that is part of the appeal to me. Like the aforementioned Gourami species...Many come from (often temporal) very acidic, sluggish, peat swamps and rivulets choked with leaves and botanical materials...right up our alley, huh? And they are usually non-competitive feeders, possibly due to their diminutive size. And as little fishes, they generally tend to stay in small physical areas, typically not straying far from a single spot. These types of habits are a neat clue for us to use when figuring out how to care for them.

I recently experimented with a small tank specifically to test a "proof of concept" for the diminutive "Green Neon Tetra", Paracheirodon simulans. It was intended not only to see how a small shoal of these little guys would do as the sole residents of a  specialized tank- it was designed to test the concept of a "pure leaf litter" style of tank. That is, a tank with no other botanical or hardscape materials except some leaves and a few twigs. 


Not only did the tank look different than any other blackwater, botanical-style aquarium I've ever played with- it functioned differently as well. It gave me some "hands-on" experience in managing such a specialized botanical-style blackwater system, in terms of water quality, biological/chemical stability, and stocking. It also gave me a chance to experiment with the idea of "non-feeding"- letting the fishes feed solely off of the micro/macro fauna that developed within the decomposing litter bed.

It was a highly successful experiment, too. Not only has it been biologically stable, with no detectable nitrate or phosphate accumulation over the 120-plus days it's been in operation, it has been interesting from a "fish-keeping" standpoint. The tight, yet relaxed shoaling behavior of the little Simulans has been really fascinating to watch, with a tremendous amount of socialization, and what almost seems like "cooperative grazing" behavior on the biofilms and other food sources  accumulating on the leaves.

Little fishes. Little tanks. Big ideas. A formidable combo, IMHO. 

Yeah, little guys.

The saving grace for fishes like this, from a typical hobbyist's standpoint, is that you CAN legitimately house them correctly in a small aquarium. In this instance, a small aquarium provides ease of environmental control, puts the fishes "closer to the food", and gives you a more concentrated field of view in which to observe them carefully- a real plus with tiny fishes!

Now, sure, you absolutely could keep them in a large tank...Yet, I think these types of fishes make a good case for the so-called "Nano-sized" aquariums. Again, this desire to help facilitate such experiments is precisely why we are offering smaller aquariums from the Ultum Nature Systems line.

So much has been written on "nano fishes" that it's hardly worth discussion here; suffice it to say, they are ideal subjects for us to play with. 

I think the broader context here is that there has never been a better time for  experimentation with fishes that would otherwise be overlooked in larger aquariums. 

The possibility of simulating specialized small habitats and executing them on a small scale is really interesting. Start by researching jungle stream or pool ecology. Learn which fishes are found in them. Try replicating those super-shallow aquatic environments with nano tanks. Keep the water in the tank shallow. Add leaves and stuff.

Observe. Explore. Enjoy. 

Another thing on my radar is the idea of biological diversity and variety in aquariums, and I think that the idea of utilizing botanical materials as we do certainly creates diversity in terms of "enrichment" of the aquatic habitat, and for providing a "substrate" for breeding fishes and other organisms, ranging from fungi to aquatic crustaceans.

I often postulate that a botanical "bed" in an aquarium functions much as a refugium does in a marine aquarium...yet the idea of perhaps setting up a freshwater refugium of sorts utilizing botanicals (or not) is still appealing to me.

The idea of creating a small aquarium that, in essence, functions like a refugium would be to experiment with one as a fry growout or rearing tank. The biologically rich system could be "pre-inoculated" with all sorts of microorganisms (I"m thinking creatures like Paramecium, various "infusoria", rotifers, etc.), that would utilize the decomposing leaves and botanicals as a food source.

Not an "exact science", or even a primary feeding scheme, but the ultimate supplemental feeding concept, which might help support growth of some of the aforementioned small fishes, such as characins, Danios, Gouramis, etc. in early growout phases.

Or, perhaps even as adults, right? 

The concept is not all that different than the "densely planted rearing tanks" of my childhood that I kept killies and livebearers in- places for fishes to get a good start on life; feeding freely on natural foods in a protected environment.

I find these types of small concept tanks really intriguing, not only in terms of supporting specific fishes- but for generalized aquarium keeping.

That's in everyone's "sphere of obsession!"

Stay inquisitive. Stay experimental. Stay bold. Stay observant...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


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