July 02, 2020

Shallow thoughts...

I suppose tastes change in the hobby over time...I certainly know that MINE do!

For example, my feelings about small tanks have come full-circle over the years. I've really come to enjoy them- for a lot of reasons, really...not the least of which is that they can serve as a sort of reliable and easy-to-iterate "test bed" for lots of new ideas.

In particular, lately I'm really fond of shallow, rather wide aquariums. The unique dimensions of such tanks gives you interesting possibilities to create simple, yet utterly fascinating displays.

And of course, this makes some sense when you contemplate the types of aquatic habitats I'm drawn to. Like, here at Tannin, we're crazy about small, shallow bodies of water, right?

Especially little rivulets, vernal pools, creeks, and forest streams.

The kinds which have an accumulation of leaves and botanical materials on the bottom. The environments which are often shaded, loaded with twigs, and replete with tinted water...

You know, the kind where you'll find fishes!

Happily, such interesting aquatic habitats exist all over the world, leaving us no shortage of inspiring places to attempt to replicate.

In Africa. many of these little streams are home to some of my fave fishes, killifish!

As mentioned above, these little jungle streams are really shallow, cutting gently through accumulations of leaves and forest debris. Many are seasonal. The great killie documenter/collector, Col. Jorgen Scheel, precisely described the water conditions found in their habitat as, "...rather hot, shallow, usually stagnant & probably soft & acid."

Ah-ah! We know this territory pretty well, right?

I think we do...minus the "stagnant" part, of course...

And understanding this type of habitat has lots of implications for creating very cool biotope-inspired aquariums.

And why not make 'em for killifish?

So, for the most part, these fishes are often found in very shallow jungle streams. How shallow? Well, reports I've seen have stated that they're as shallow as 2 inches (5.08cm). That's really shallow. Seriously shallow! And, quite frankly, I'd call that more of a "rivulet" than a stream! "Virtually still, with a barely perceptible current..." was one description.

That kind of makes my case.

What does that mean for those of us who keep small aquariums?

Well, it gives us some inspiration, huh? Ideas for tanks that attempt to replicate and study these compelling shallow water environments...

Now, I don't expect you to set up a tank with a water level that's 2 inches deep..Well, it would be pretty cool...Yet, that's kind of extreme. For more of us, perhaps a 3.5"-4" (8.89-10.16cm) deep depth is something that can work? Totally doable. There are some pretty small commercial aquariums that aren't much deeper than 8" (20.32cm), and you could adapt other containers for this purpose, right?

We could do this with some of the very interesting South American or Asian habitats, too...Shallow tanks, deep leaf litter, and even some botanicals for good measure.

Fishes like "Darter characins" and the like can do very well in such conditions. In fact, many small tetras can. If you remember, we ran a very successful "all leaf litter" tank with the "Green Neon Tetra" a while back, and it was one of the most interesting systems I've ever played with.

I only filled this tank to a depth of around 5 inches ( 12.7cm) at the most. But I used a lot of leaves to cover the bottom. I used "Texas Live Oak Leaf Litter", "Nano" Catappa leaves, and Yellow Mangrove leaves. The result was a deeply tinted aquarium with very little in the way of vertical relief. At first, you'd think this would be just incredibly boring.

It wasn't.

The fishes were not only stunning to look at against this interesting "substrate", they displayed a remarkable set of behaviors, such as a "cooperative foraging" among the leaves, with every individual in the shoal taking part- that I had not seen before. Some would dive in and pick at "something", while the remainder would sort of "hold station" above the leaves. This behavior would go on for hours! It was neat to watch.

I've often fantasized about a long, low, shallow aquarium with just a fine sand substrate and a few pieces of driftwood- perhaps an interesting habitat for Corydoras or other small catfishes. I've seen images of habitats like this from our friend, David Sobry, taken in The Amazon- and they're quite compelling!

Even the idea of a near "wood-free" shallow stream, with riparian vegetation on the "banks" would be fascinating to recreate in the aquarium. Utilizing a correctly-sized aquarium would deliver a unique look, above and below the water surface.

And of course, the tropical habitats of the world don't limit you to sand and branches and leaves for your "hardscape..." You can also create very interesting rock-based systems, right?

Again some "Darter characins" (Characidium sp.) would work in such an aquarium, as would Hillstream loaches and other interesting fishes in habitiats designed to replicate Asian biotopes. There is a lot of interesting stuff to take away from these habitats.

Streams are really amazing habitats for us to play with. There is so much interesting stuff to take away from them. And a whole science to their structure and function that is filled with takeaways for the aquarist.

The definition of a "stream" is: "...a body of water flowing in a channel or watercourse, as a river, rivulet, or brook..."

And of course, these little bodies of water flow through jungled areas, where they're bound to pick up some leaves, twigs, and other plant parts as they wind along their path. Leaves, the "jumping off point" of our botanical obsession, form a very important part of these stream habitats.

It is known by science that the leaf litter and the community of aquatic animals that it hosts is, according to one study, "... of great importance in assimilating energy from forest primary production into the blackwater aquatic system."

It also functions as a means to preserve the nutrients that would be lost to the forests which would inevitably occur if all the material which fell into the streams was simply washed downstream. The fishes, crustaceans, and insects that live in the leaf litter and feed on the fungi, detritus, and decomposing leaves themselves are very important to the overall habitat.

In the aquarium, leaf litter and botanicals certainly perform a similar role in helping to sequester these materials.

Some litter beds form in what stream ecologists call "meanders", which are stream structures that form when moving water in a stream erodes the outer banks and widens its "valley", and the inner part of the river has less energy and deposits silt- or in our instance, leaves.

There is a whole, fascinating science to river and stream structure, and with so many implications for understanding how these structures and mechanisms affect fish population, occurrence, behavior, and ecology, it's well worth studying for aquarium interpretation! Did you get that part where I mentioned that the lower-energy parts of the water courses tend to accumulate leaves and sediments and stuff?

It's logical, right?

And it's also interesting, because, as we know, fishes and their food items tend to aggregate in these areas, and embracing the "theme" of a litter/botanical bed or even wood placement, in the context of a stream structure in the aquarium is kind of cool!

The big takeaway here?

Research jungle stream or pool ecology. Study images and videos of these natural habitats. 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.