When a tree falls, an aquatic habitat rises up...


I think that if you ask most aquarists, they'll tell you that the basis for almost any aquascape has to be wood of some sort. And it makes sense. Wood adds a sense of color, texture, and depth to any aquascape. It makes or breaks it, in many cases, right?

A good part of the aquarium "practice" is the use of various types of wood. Hobbyists have actively sought out and used all sorts of wood for use in aquascaping pretty much as long as the hobby has been around! 

And why not?

And of course, branches and twigs and other tree parts are ubiquitous in the wild aquatic environments of the world.  And many of you are absolutely incredible at 'scaping with wood! Collectively, we've developed extreme talent for creating fantastic designs with all sorts of wood.

However, have you ever noticed that most of the wood we use is more of the "branchy" type, and not anything reminiscent of say, a tree trunk or very large branch?

It is 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 that I'm totally obsessed with, they fall and are submerged in the inundated forest floor when the waters return.

And of course, they immediately impact their (now) aquatic environment, fulfilling several functions: Providing a physical barrier or separation from currents, offering territories for fishes to spawn in,  providing a substrate for algae and biofilms to multiply on, and providing places for fishes forage among, and hide in. An entire community of aquatic life forms uses the fallen tree for many purposes. And the tree trunks and parts will last for many years, fulfilling this important role in the aquatic ecosystems they now reside in each time the waters return.

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  fallen 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.  

These materials are known as “coarse particulate organic matter”, and in the waters of these inundated forest floors there is a lot of CPOM, and 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" (FPOM).

And of course, some fishes, like larger characins, catfishes, etc., 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!

Yeah, that detritus.

The stuff of nightmares for many dyed-in-the-wool hobbyists...the stuff of dreams for many fishes who consume it and the associates fauna within it.

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. 

We see similar results in our aquariums, right?

And of course, the tree, like almost anything that is submerged,  will gradually decompose over long periods of time. This process is actively exploited by aquatic life forms at all levels. Hollowed-out sections will be inhabited by fishes and exploited for the shelter they offer, and of course, the aforementioned crustaceans and insects will utilize the tree in various ways.

And interestingly, when you think about it, fish movement and species richness and population is directly affected by the physical and biological influences of... fallen trees! And the deep beds of leaves that may be "corralled" by the fallen trees- a sort of natural "dam"- will definitely 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 to their environment caused by fallen trees!

It's pretty hardcore stuff. And pretty fascinating.

So, as aquarium hobbyists, what does this all mean to us? How can we employ the lessons learned from fallen trees in nature? What can we do to mimic this?

Well, for one thing, I think it's a call for us to consider employing 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 they're likely not as sexy as those awful "bonsai trees" that are (regrettably) becoming popular again...And, of course, a big, heavy piece of wood is kind of...pricy.

And physically cumbersome for some.

In fact, there are many who would make the case that you can't make big gnarly pieces of wood "work" in an aquarium because of their impact on "ratio" and "proportion", etc...And to these types, I gently admonish you to return to your world of "fantasy floating forests", underwater beach scenes, and "Middle Earth" dioramas that you guys drool over at the international competitions, and leave the replication of nature to those hobbyists who think for themselves and occasionally choose step off the well-trodden, popular path. Besides, you wouldn't want to see leaves and brown water in there, right? It's...not...perfectly neat and orderly... Good heavens!

Okay, that was bit harsh...a mini-thrashing from me again..but it's an honest sentiment. I mean, be open minded!

Almost a "prerequisite" of late when I talk about any idea that has an aesthetic component to it, because the self-appointed "guardians of aquascaping style" seem to come out of the woodwork (lol) after these discussions, reciting dozens of well-rehearsed reasons why the concept won't work, rather than even trying to do something similar. It's weird. 

What can I say?

Yes, a big piece of wood in an aquarium does create some challenges, but most of them are in our head. Hell, Amano himself did a few amazing tanks with huge pieces of wood years ago.

And of course, a large piece 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?


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.

Populate the system with food orgmaisms, 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", if you really take a good look at it.

So, yeah.

Trying what might appear to be a big, somewhat awkward piece of wood or group of pieces- 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...

However, 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 of that big, gnarly tree trunk 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.

Mental shift...A little bit, right.

Make it.

So, a tree may go down...And an awful lot of good stuff starts happening underneath the water!


Yeah, I think so.

Stay adventurous. Stay inventive. Stay creative. Stay inspired. Stay undaunted. Stay relentless.

And Stay Wet.

Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


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