The "terrestrial transformation" and its implications for our aquariums...

We spend much time here discussing the implications of terrestrial environments meeting-or becoming- aquatic habitats after periods of inundation. It's particularly significant in those igapo habitats in South America.

Many other fishes which reside in these flooded forest areas feed mainly on insects; specifically, small ones, such as beetles, spiders, and ants from the forest canopy. These insects are likely dislodged from the overhanging trees by wind and rain, and the opportunistic fishes are always ready for a quick meal!


Interestingly, it's been postulated that the reason the Amazon has so many small fishes is that they evolved as a response to the opportunities to feed on insects served up by the flooded forests in which they reside! The little guys do a better job at eating small insects which fall into the water than the larger, clumsier guys who snap up nuts and fruits with their huge mouths! 

And, yes, many species of fishes specialize in consuming detritus.

As we know by now, decomposing leaves are the basis of the food chain, and the detritus they produce forms an extremely important part of the food chain for many, many species of fishes. Some have even adapted morphologically to feed on detritus produced in these habitats, by developing bristle-like teeth to remove it from branches,tree trunks, plant stems, and leaf litter beds. 

Of course, it's not just the fishes which derive benefits from the terrestrial materials which find their way into the water. Bacteria, fungi, and algae also act upon the nutrients released into the water by the decomposing organic material from these plants. Aquatic plants (known collectively to science as macrophytes) grow in or near water and are either emergent, submergent, or floating, and play a role in "filtering" these flooded habitats in nature.

Terrestrial trees also play a role in removing, utilizing, and returning nutrients to the aquatic habitat. They remove some nutrient from the submerged soils, and return some in the form of leaf drop. 

Interestingly, studies show that about 70% of the leaf drop from the surrounding trees in the igapo habitats occurs when the area is submerged, but the bulk of it is shedded at the end of the inundation period. The falling leaves gradually decompose and become part of the detritus in the food web, which is essential for many species of fishes. This "late-inundation leaf drop" also sets things up for the "next round" - providing a "starter" of nutrients !

Our ability to mimic this aspect of the flooded forest habitats is a real source of benefits for the fishes that we keep- and a key to unlocking the secrets to long-term maintenance and husbandry of botanically-influenced aquariums.

The transformation of dry forest floors into aquatic habitats provides a tremendous amount if inspiration AND biological diversity and activity for both the natural environment and our aquariums.

Flood pulses in these habitats easily enable large-scale "transfers" of nutrients and food items between the terrestrial and aquatic environment. This is of huge importance to the ecosystem. As we've touched on before, aquatic food webs in the Amazon area (and in other tropical ecosystems) are very strongly influenced by the input of terrestrial materials, and this is really an important point for those of us interested in creating more natural aquatic displays and microcosms for the fishes we wish to keep.

Creating an aquascape utilizing a matrix of leaves, roots, and there materials, is one of my favorite aesthetic interpretations of this habitat...and it happens to be supremely functional as an aquarium, as well! I think it's a "prototype" for many of us to follow, merging looks and function together adeptly and beautifully.

Study this one...

Now, I think at least part of the reason why we're seeing success with utilizing botanicals in our aquariums is that fishes are instinctively "programmed" to utilize many of these materials as both feeding substrates- and as food items in and of themselves. (Yeah, "pellets and flakes" are NOT part of their natural diet... 😆)

The addition and replenishment of leaves and other botanical materials which we execute in our tanks definitely mimics, at least to some extent, the processes which occur in these habitats which transfer food and nutrients into the aquatic habitat.

And with the ability to provide live foods such as small insects (I'm thinking wingless fruit flies and ants)- and to potentially "cultivate" some worms (Bloodworms, for sure) "in situ"- there are lots of compelling possibilities for creating really comfortable, natural-appearing (and functioning) biotope/biotype aquariums for fishes.

I admit, that I sometimes fear that the burgeoning interest in biotope aquariums at a "contest level" will result in the same sort of "diorama effect" we've seen in planted aquarium contests. In other words, just focusing on the "look" (which is cool, don't get me wrong) yet summarily overlooking the reason why the habitat looks the way it does and how fishes have adapted to it...and considering how we can utilize this for their husbandry, spawning, etc.

I'm sure it's unfounded, but until very recently, it seems to me that the hobby has traditionally overlooked the real function of nature, so there is some precedent, unfortunately. I hope that "biotopers", who have a lot of awareness about the habitats they are inspired by, will at least consider this "functional/aesthetic" dynamic that we obsess over when they conceive and execute their work. 

It should go beyond merely creating the "look" of these systems to win a contest, IMHO. Rather, we should also focus on the structural/functional aspects of these environments to create long-term benefits for the fishes we keep in them.

That's a real "biotope aquarium" in my book.

And the emphasis on long-term is important. If we're setting up tanks just to function as "kinetic art" for just a few weeks or a couple of months to win in a contest, as opposed to setting up systems to operate over a long term, we're totally blowing a great opportunity to advance the art and science of aquarium-keeping!

Don't blow it! 

Leaves, detritus, submerged terrestrial plants- all have their place in an aquarium designed to mimic these unique aquatic habitats.  You can and should be able to manage nutrients and the bioload input released into our closed systems by these materials, as we've discussed (and executed/demostrated) here for years.  The fear about "detritus" and such "crashing tanks" is largely overstated, IMHO- especially with competent aquarium husbandry and proper outfitting of a tank with good filtration and nutrient control/export systems in place.

We've talked about this many times here in "The Tint."

If you're up to the challenge of attempting to replicate the look of some natural habitat- you should be a competent enough aquarist to be able to responsibly manage the system over the long term, as well.

Ouch, right?

 Hey, that's reality. Sorry to be so frank. Enough of the "shallow mimicry" mindset that has dominated the aquascaping/contest world for too long, IMHO. You want to influence/educate people and inspire them? Want to really advance the hobby and art/science of aquarium keeping? Then execute a tank which can be managed over the long haul. Crack the code. Figure out the technique. Look to Nature and "back engineer" it. These things can be done. 

There are many aspects of wild habitats that we choose to replicate, which we can turn into "functionally aesthetic" aquarium systems. Let's not forget the trees themselves- in their submerged and even fallen state! These are more than just "hardscape" to those of us who are into the functional aesthetic aspects of our aquariums.

Yeah, literally not overlooking the trees...and all of the materials which are derived from them- and how they influence the aquatic habitats that we admire so much.

A challenge- a good one- to all who venture into our little corner of the hobby.

Go for it!

Stay creative. Stay studious. Stay diligent. Stay consistent. Stay engaged...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

May 05, 2019

Yep- you got it! Always a reason for another tank! That’s why we are fish geeks, right? On the other hand, a well-managed single tank could accomplish the same “transformation”, but where’s the fun in having just ONE tank?


Bengt L. Åkesson
Bengt L. Åkesson

May 03, 2019

So I need, not only one but two aquariums;
one for the dry season and an other for the overflooded season.
After six month it´s time to switch – water and fishes to the dry season aquarium and let the other aquarium stay dry (with a little pond inside it).
Both aquariums need plants that can be in water or without water.

I can´t write down all but You now the rest and what to do.
[parden my english]

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