December 29, 2018

More wood. More ideas?

Wood is definitely a focal point of our aquaecapes. It gives power, depth, texture, contrast, and a certain "presence" to our scapes. And many of you are absolutely incredible at 'scaping with wood! Most of the best aquascapes in the world incorporate wood to varying degrees.

However, have you ever noticed that most of the wood we tend to use is more of the "branchy" type, and not anything reminiscent of say, a tree trunk or very large branch? And we tend to leave a lot more negative space in our scapes as a result?

And this always strikes me as a bit odd, because in nature, it's a lot more common to see streams and rivers filled with fallen trees or larger branches.

And it's not uncommon at all for small (and large) trees to fall in the rain forest, with punishing rain and saturated ground conspiring to easily knock over anything that's not firmly rooted. When these trees fall over, they often fall into small streams, or in the case of the varzea or igapo environments in The Amazon, they fall and are submerged in the inundated forest floor during the wet season.

And of course, they immediately impact the (now) aquatic environment, fulfilling several functions: Providing a physical barrier or separation from currents, offering territories for fishes to spawn in, forage among, and hide in. An entire community of aquatic life forms uses the fallen tree for many purposes. And they will last for many years, fulfilling this important role in the aquatic ecosystems they now reside in.

What happens when a tree falls into the water? It's a familiar story to us as aquarists, right? Shortly after falling into the water, fungi and other microorganisms act to colonize the surfaces, and biofilms populate the bark and exposed surfaces of the tree. Over time, the tree will impart many chemical substances, (humic acids, tannins, sugars, etc.) into the water.

The tree literally brings new life to the waters.

The materials that comprise the tree are known in ecology as "allochthonous material"- something imported into an ecosystem from outside of it. (extra points if you can pronounce the word on the first try...) And of course, in the case of fallen trees, this includes includes leaves, fruits and seed pods that fall or are washed into the water along with the branches and trunks that topple into the stream.

Ahh...sounding familiar, huh?

These materials are known as “coarse particulate organic matter”, and in the waters of these inundated forest floors there is a lot of CPOM. The community of aquatic organisms (typically the aforementioned aquatic insects and crustaceans) has a high proportion of “shredders”, which feed on the CPOM and break it up into tinier bits called...wait for it... fine particulate organic matter.

And of course, some fishes directly consume fallen fruits and seeds as part of their diet as well, aiding in the "refinement" of the CPOM. Other organisms make use of the fine particulate matter by filtering it from the water or accessing it in the sediments that result. These allochthonous materials support a diverse food chain that's almost entirely based on our old friend, detritus!

And, although the forest floor receives substantially less sunlight than open rivers, the nutrients and available light are utilized by algae, which may colonize the surfaces facing up into the sun. Algal mats which arise from these fallen trees form an important food source and grazing area for many fishes.

And of course, the tree will gradually decompose over long periods of time. Hollowed-out sections will be inhabited by fishes and exploited for the shelter they offer throughout the duration (many years) that the tree is present in the water.

And interestingly, when you do some research, you'll find that scientists have learned that fish movement and species richness- and population- are all affected by the physical and biological influences of fallen trees! And, in the wild, the deep beds of leaves that may be "corralled" by the fallen trees- a sort of natural "dam"- will actually limit some fish species, which cannot tolerate the lower oxygen concentrations found in these areas.

Other fishes take advantage of the physical barrier that a fallen tree presents to shelter from predatory species. Many adaptations have taken place over eons to allow fishes to exploit these changes in their environment caused by fallen trees!

It's pretty hardcore stuff.

So, as aquarium hobbyists, what does this all mean to us?

Well, for one thing, I think it's a call for us to employ some bigger, thicker pieces of wood in our tanks! Now, sure, I can hear some groans. I mean, big, heavy wood has some disadvantages in an aquarium. First, the damn things are...well- BIG- taking up a lot of physical space, and in our case, precious water volume. And the "scale" is a bit different. And, of course, a big, heavy piece of wood is kind of pricy. And physically cumbersome for some.

Of course, you can use a few smaller pieces of wood to create a single large structure...Lots of ways to be creative and economical.

Yes, a big piece of wood or aggregation of wood pieces in an aquarium does create some challenges, but most of them are in our head. And of course, a large aggregation of wood relative to water volume has a chemical and physical impact on the aquatic environment that is...hey- sort of similar to that which occurs in nature, right?

Yeah.

Try a fairly large piece of aquatic wood (or several smaller pieces, aggregated to form one big piece) some time. Arrange it in such a way as to break up the tank space and give the impression that it simply fell in naturally. Let it create barriers for fishes to swim into, disrupted water flow patterns, and small pockets where leaves, botanicals, substrate materials, and...detritus can collect.

Yeah. encourage it.

Populate the system with food organisms, like Daphnia, Gammarus, and the like, weeks or months before you add the fishes. Enjoy the biofilms. And select a population of fishes that can exploit the variety of new habitats that the "fallen tree" creates.

There are many distinct "zones" which a larger piece, or pieces of wood create, if you really take a good look at it- and lots of fishes make use of them.

So, yeah.

Trying what might appear to be a big, somewhat awkward piece of wood filling much of the tank can be a challenge to our aesthetic sensibilities at first. But guess what? You'll get over it when you simply enjoy the setup for what it represents- not for a "typical" aquascape. And, when you populate the tank correctly, with fishes that can utilize the interesting ecological niches within the tank, you'll realize that "conventional" aquascaping is not the only way...

Of course, hobbyists have been throwing big old wood pieces into tanks for decades...But I don't think that we've "played it out" in a manner that took advantage of the relative uniqueness of the concept. That is, we haven't really thought through the idea that a big, gnarly tree trunk or aggregation of large pieces in our tank functions not only as an aesthetic component, but more important- as an ecosystem, which supports not only an abundance of life, but provides a tremendously interesting study in adaptation and the resourcefulness of nature.