November 07, 2018

Water, soil, botanicals, and fishes. Interdependencies and interactions...

Have you ever noticed how some subjects in the botanical-style aquarium world just keep coming up over and over again? Like, you'll look at things from a different angle, or with the benefit of experience, and suddenly something that seemed odd or inconsequential before is compelling, exciting, and potentially very significant.

One of those subjects we've explored before is the idea of utilizing more natural substrate materials in our botanical-style aquariums, such as clays, as opposed to more "traditional" gravels and sands. And we're lucky- with the popularity of plants and shrimp, we've seen a proliferation of "specialty" substrates that could really benefit the kind of work we do, too! I often ponder which types would be interesting to use with botanicals to create rich and productive aquatic environments.

And of course, to figure this out, I look towards nature...

Like, where do our coveted blackwater originate?

In general, blackwaters originate from sandy soils. High concentrations of humic acids in the water are thought to occur in drainages with what scientists call "podzol" sandy soils. "Podzol" is a soil classification which describes an infertile acidic soil having an "ashlike" subsurface layer from which minerals have been leached. That last part is interesting, and helps explain in part the absence of minerals in blackwater. And more than one hobbyist I know has played with the concept of "dirted" planted tanks, using terrestrial soils...hmmm.

On to something here!

Also interesting to note is that fact that soluble humic acids are adsorbed by clay minerals in what are known as "oxisol" soils, resulting in clear waters."Oxisol" soils are often classified as "laterite" soils, which some who grow plants are familiar with, known for their richness in iron and aluminum oxides. I'm no chemist, or even a planted tank geek..but aren't those important elements for aquatic plants?

Yeah...I think they are.

And, in "iagapos "(those seasonally flooded forest areas which lead to blackwater environments), the soils are conducive to good terrestrial plant growth. Fishes which reside in these habitats feed off of the materials, like fruits and seeds, which fall from the trees, or otherwise end up in the water during periods of inundation.

Interestingly, seed dispersal by fish (a process known technically as "ichthyochory") is thought to play an important role in the maintenance of the diversity of trees in these seasonally inundated forests along the main rivers of the Amazon.

An interesting little tidbit of information! The terrestrial environment has significant impact on the aquatic habitat. And, in this area, aquatic life influences the land!

That makes sense, right?

Fishes which consume matter found in the substrate (detritivores) and other materials in the substrate (omnivores) also play a fundamental role in the transportation of organic carbon, which is a source of energy for downstream fish communities. Through their foraging activities, these fishes enhance the "downstream transport" and processing of organic material and ensure the proper functioning of the aquatic system and its biological community.

So, we have the terrestrial environment influencing the aquatic environment, and fishes that live in the aquatic environment influencing the terrestrial environment!

These interdependencies are really complicated- and really interesting!

And it just goes to show you that some of the things we could do in our aquariums (such as utilizing alternative substrate materials, botanicals, and perhaps even submersion-tolerant terrestrial plants) are strongly reminiscent of what happens in the wild. Sure, we typically don't maintain completely "open" systems, but I wonder just how much of the ecology of these fascinating habitats we can replicate in our tanks-and what potential benefits may be realized?

That's my continuing challenge to our community...We're seeing so many hobbyists being drawn to "the dark side"- botanical-style, blackwater aquariums because of the compelling aesthetic, and potential collateral health benefits they provide to our fishes. Yet, there is so much more! Exploring ideas like these give us the opportunity to examine other possible benefits that we may not have even considered just yet!