As hobbyists, we spend a pretty good amount of time studying, scheming, and pondering how to create a compatible, interesting, and attractive community of fishes within our aquariums.
As a somewhat eccentric philosopher of all things fish, one of my favorite things to ponder is stuff that we do in creating aquariums that is- intentionally or otherwise- analogous to the factors in nature that result in the environments and fish populations that we find so compelling.
When we create our aquariums, we take into consideration a lot of factors, ranging from the temperament and size of our fish selections, to their appearance, right? These are all important factors. However, have you ever considered what the factors are in nature which affect the composition of a fish community in a given habitat? Like, why "x" fish is living in "such and such" a habitat? What adaptations has the fish made that make it uniquely suitable for this environmental niche? Further, have you thought about how we as hobbyists replicate, to some extent, the selection processes which occur in nature in our quest to create the perfect community aquarium?
Now, if you're an African Cichlid lover or reef hobbyist, I'm sure you have! Social hierarchies and spatial orientations are vital to success in those types of aquariums; you typically can't get away with just throwing in a random fish or coral and hoping it will mix okay. However, for many hobbyists who aim to construct simple "community tanks", it isn't that vital to fill specific niches and such...we probably move other factors to the forefront when thinking about possible additions to our community of fishes. Like, how cool the fish looks, how large it grows, if it has a peaceful temperament, etc. More basic stuff. However, in the end, we almost always make selections based upon factors which we deem important...again, a near-mimicry of natural processes- and how the fishes work in the habitat we've created for them.
"Unnatural selection?" Or...
What exactly is an "aquatic habitat", by the way? In short, you could say that an aquatic habitat is the physical, chemical, and biological characteristics which determine the suitability for habitation and reproduction of fishes. Of course, these characteristics can determine which fishes are found in a given area in the wild without exception.
Approaching the stocking of an aquarium by determining which fishes would be appropriate for the physical characteristics of the tank is not exactly groundbreaking stuff. However, when we evaluate this in the context of "theme", and what fish would be found within, say, an Amazonian Igarape stream, the idea of adding fishes to "exploit" the features of the habitat we've created is remarkably similar to the processes which occur in nature that determine what fish are found there, and it's the ultimate expression of good tank planning, IMHO.
It's just kind of interesting to think about.
Competition is one of the important factors in determining fish populations in the wild. Specifically, competition for space, resources (e.g.; food) and mates are prevalent. In our aquariums, we do see this to some extent, right? The "alpha male" cichlid, the Pleco that gets the best cave, and the Tetra which dominates his shoal. How we create the physical space for our fishes can have significant impact on this behavior. When good hiding spaces are at a premium, as are available spawning partners, their will be a social hierarchy, won't there?
Other environmental factors, such as water movement, dissolved oxygen, etc. are perhaps less impactful on our community once the tank is established. However, these factors figure prominently in our decisions about the composition of the community, don't they? For example, you're unlikely to keep Hillstream loaches in a near stagnant, blackwater swamp biotope aquarium, just like you'd be unlikely to keep Altum Angelfish in a fast-moving stream biotope representation.
One factor that we typically don't have in our aquaria is predation. I know very few aquarist sadistic enough to try to keep predators and prey in the same tank, to let them "have at it" and see what happens, and who comes out on top!
I mean, there is a lot to this stuff. Again, the idea of creating a tank to serve the needs of certain fishes isn't earth-shattering. Yet, the idea of stocking the tank based on the available niches and physical characteristics is kind of a cool, educational, and ultimately very gratifying process. I just think it's cool that we're able to do this these days.
Fun to think about on a Saturday morning.
Have a great weekend.
Stay excited. Stay thoughtful. Stay engaged.