February 26, 2019

"Like Nature in Form and Function..."

I was playing with a small tank the other day, in a rare moment of fish geek "free time" I created, and I was playing with (of course) some leaf litter, within a "bramble" (for want of a better word) of wood. And setting in the leaves, which is pretty much a theme of mine in every tank, I recalled the studies I've done on how botanical materials distribute themselves in natural aquatic habitats.

And this is something to consider in aquarium keeping, particularly for those of us who embrace the idea of creating simulations of these wild habitats. There are a few considerations, believe it or not-including simply how they "fall" in our aquascapes, and the impact which they have on our fishes while they're physically present in our aquariums.

And it's important to recognize the fact that a bed of leaves and botanicals on the bottom of your tank is not just a "static" part of the aquarium. Fish movement, current, and the random movement that occurs when you accidentally redistribute botanicals in your aquariums during maintenance, you create unique new "microhabitats" for your fishes. And that's exactly like what occurs in Nature.

A simple thought- but profoundly important, really. And readily apparent to all who play with leaves and botanicals. Something to think about and consider.

I love this topic (and fortunately, a lot of hobbyists like you are as geeked-out as I am about it, too!) because it's one of those things that most of us don't even think of in terms of our aquariums, and it's only now becoming a "thing" as more of us play with these materials! The idea of actual "beds" of leaf litter and such on the bottom of our aquariums, although not some quantum leap in aquarium keeping, hasn't been discussed all that much over the years.

When you think about how materials "get around" in the wild aquatic habitats, there are a few factors which influence both the accumulation and distribution of them. In many topical streams, the water depth and intensity of the flow changes during periods of rain and runoff, creating significant re-distribution of the materials which accumulate on the bottom, such as leaves, seed pods, and the like.

Larger, more "hefty" materials, such as submerged logs, etc., will tend to move less frequently, and in many instances, they'll remain stationary, providing a physical diversion for water as substrate materials accumulate around them.

A "dam", of sorts, if you will. And this creates known structures within streams in areas like Amazonia, which are known to have existed for many years. Semi-permanent aquatic features within the streams, which influence not only the physical and chemical environment, but the very habits and abundance of the fishes which reside there.

Most of the small stuff tends to move around quite a bit... One might say that the "material changes" created by this movement of materials can have significant implications for fishes. In the wild, they follow the food, often existing in, and subsisting off of what they can find in these areas.

the case of our aquariums, this "redistribution" of material can create interesting opportunities to not only switch up the aesthetics of our tanks, but to provide new and unique little physical areas for many of the fishes we keep.

The benthic microfauna which our fishes tend to feed on also are affected by this phenomenon, and as mentioned above, the fishes tend to "follow the food", making this a case of the fishes learning (?) to adapt to a changing environment. And perhaps...maybe...the idea of fishes sort of having to constantly adjust to a changing physical (note I didn't say "chemical") environment could be some sort of "trigger", hidden deep in their genetic code, that perhaps stimulates overall health, immunity or spawning?

Something in their "programing" that says, "You're at home..." Triggering specific adaptive behaviors?

I find this possibility fascinating, because we can learn more about our fishes' behaviors, and create really interesting habitats for them simply by adding botanicals to our aquariums and allowing them to "do their own thing"- to break apart as they decompose, move about as we change water or conduct maintenance activities, or add new pieces from time to time.

Again, much like Nature.

Like any environment, leaf litter beds have their own "rhythm", fostering substantial communities of fishes. The dynamic behind this biotope can best be summarized in this interesting excerpt from an academic paper on Blackwater leaf-litter communities by biologist Peter Alan Henderson, that is useful for those of us attempting to replicate these communities in our aquaria:

"..life within the litter is not a crowded, chaotic scramble for space and food. Each species occupies a sub-region defined by physical variables such as flow and oxygen content, water depth, litter depth and particle size…

...this subtle subdivision of space is the key to understanding the maintenance of diversity. While subdivision of time is also evident with, for example, gymnotids hunting by night and cichlids hunting by day, this is only possible when each species has its space within which to hide.”

In other words, different species inhabit different sections of the leaf litter, and we should consider this when creating and stocking our aquariums. It makes sense, right?

The big takeaway: A leaf litter bed is a physical structure, temporal though it may be- which functions just like a hardscape of wood, a reef, rocks, or other features in the benthic environment, although perhaps "looser" and more dynamic.