October 16, 2018

Just like in nature? Sort of? Yeah...

Have you ever considered that an aquarium is, at best, a facsimile of a natural system? I mean, at the very least, we are getting pretty good at making our tanks look like many of the natural systems that we admire...but it goes even deeper than that- and we may not even consider how we in the blackwater, botanical-style aquarium community take it to another level.

It seems like we talk a lot here about the idea of "food webs" and "holistic" aquariums, but I think that's an important pair of concepts to think about. For decades, the aquarium hobby has been about establishing a tank by allowing the benefcial bacteria to colonize the filter and substrate, so that they can perpetuate the nitrogen cycle.

We all more-or-less get that.

However, I think where we tend to differ from the masses in the hobby in our botanical-style approach is that we are replicating- wether we know it or not- another part of the dynamic tropical ecosystems: Some aspects of the "food web." Now, I say "aspects of", because it's awfully difficult- perhaps even impossible- in the confines of a closed system to have a completely self-sustaining cycle of food production without some external inputs.

But that's perfectly okay...Because what we do in our botanical-style aquarium
"practice" is almost exactly like what happens in a natural flooded forest or jungle stream: External sources (weather, etc.) deposit leaf litter and plant material into the system, spurring the growth of organisms which break it down, as well as depositing food.

Just like in nature...sort of.

There is no significant "in situ" primary production in these leaf litter, flooded forest aquatic systems. And in the aquarium-just like in nature the "food web" depends on those "allochthonous inputs" (food from outside the aquatic environment) such as fruits, plant parts, flower blossoms, leaves and wood from the surrounding forest.

At the very base of these food chains are the decomposing fungi. They help soften and begin to break down the leaves which are deposited into the water. These, in turn, are fed upon by chironomids (you know, Blood Worms!) and other small organisms, which colonize the litter.

And of course, the fishes!

Fishes are usually a little late to the party, but they show up in surprising numbers in these high diversity, low biomass systems. And these systems, just like our aquariums- are constantly changing and evolving, both in terms of their physical structure and the population of fauna. And they are, much like many aquariums, somewhat ephemeral, with more-or-less limited life spans.

An interesting passage in a paper by P.A. Henderson mentions the dynamics of fish populations and the structure of the leaf litter systems themselves in Amazonia:

"Leaf-litter banks dry out or become submerged rapidly depending

both on recent rainfall and the annual cycle of inundation. Smaller litter banks

form or disappear after sudden floods or tree falls. Even the largest banks probably

only exist for 20 to 30 years, during which their physical characteristics are con-

tinually changing. Therefore all of the litter fauna is adaptable and capable of

rapid colonization.

During high water, new habitats become available and the permanent litter

banks are deep under water where oxygen may be limiting. Many species probably

move into the forest. Recently, the young of leaf-litter fish have been caught

amongst the leaves of igapo trees and bushes, suggesting that reproduction nor-

mally occurs at high water when fish densities are much lower. Thus, within the fish fauna there exists considerable adaptability to seek

out and colonize new habitats."

I mean, unpack THAT for a few minutes...

Think about the ways in which an aquarium, specifically, a blackwater, botanical-style one- is analogous to these natural systems. The "allochthonous inputs" in our instance are the addition and replacement of botanicals, leaves...and fish food! The additions of these materials directly spur the growth of existing fungal and microorganism populations, supply supplemental food for some fishes (like detritivores and certain catfishes), and enhance the physical environment of the aquarium by providing additional hiding space and territories.

Just like in nature.

So, when you really think about it, we as practitioners of the BSBW aquarium are in a most unique position to learn first hand about how the fishes interact with and benefit from their physical environment. We control many of the variables, such as the influx of new structural materials (ie; leaves and botanicals), the nutrient inputs and exports (ie, feeding and water exchanges), and the introduction and population density of fishes in the environment.

As you surmise, some of these are things that we have done as "general" aquarists for centuries, regardless of if we were conscious about the analogy to nature or not. However, in our case, some of these practices (ie; addition, replacement, and removal of botanicals) are essentially exact duplicates of what happens in nature.

I can't help but wonder if there are any advantages to varying the routine a bit. You know, "pulsing" additions or removals of leaves and botanicals on a regular or "seasonal" basis, adding specific types of materials at certain times...or conducting larger water exchanges during the "wet" season to duplicate the "flushing" that occurs during the inundation of forests. We could even populate our systems in a sequence that sort of replicates how these habitats are populated in nature, etc.

The possibilities are endless, and the potential gains in knowledge and understanding of the wild habitats, and experience with replicating them in the aquarium are incalculable. What secrets will we unlock? What practices will yield benefits and advantages that we never even considered?

Who else is excited about this stuff?

Stay engaged. Stay thoughtful. Stay curious. Stay creative. Stay adventurous...

And Stay Wet.

Scott Fellman

Tannin Aquatics