January 27, 2021

Food production: The ultimate "collateral benefit" of the botanical-style aquarium?

We are receiving a lot of really interesting inquiries from so many hobbyists in our community regarding the "collateral" benefits of utilizing botanicals in our aquariums.

Among the most interesting and exciting one of these collateral benefits is the potential for supplemental internal food production as a result of cultivating a "bed" of leaves and other botanicals in our aquariums.

Yeah, food production.

As always, the inspiration- and "archetype" for this food production process is Nature, Herself. And one of the more fascinating habitats where food production occurs in the wild is the flooded forest floors of South America.

Now, we've talked extensively in several blog posts over the past couple of years about the idea of allochthonous input (literally, "food from the sky", lol) and how it impacts the feeding habits of many fishes, as well as their social and behavioral habits, and what could loosely be referred to as their "migratory patterns."

It's long been known that fishes which inhabit the flooded forest floors (igapo) of Amazonia, for example, tend to literally "follow the food" and move into new areas where greater feeding opportunities exist, and will even adjust their dietary preferences seasonally to accommodate the available foods.

In this instance, it typically means areas of the forest where overhanging vegetation offers falling peices of fruit, seeds, nuts, plant parts, and the occasional clumsy insect, like an ant, which falls from the branches of said vegetation. So, here is where the idea gets interesting to me: Wouldn't it make a lot of sense to create a botanical-style aquarium which not only represents the appearance of the habitat, but also replicates, to a certain extent, the function of it?

Of course it would! (Surely, you wouldn't have expected any other answer from me, right?)

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. More on that later!

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 by the trees 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. There are many takeaways for hobbyists that can be had by studying these habitats.

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 other botanical 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.

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.

And of course, when you're talking about creating a rich bed of botanicals, consisting of decomposing organic materials (leaves, coco-fiber, and other botanicals containing lignin, etc.), that creates a matrix that may eventually consist of- and perhaps accumulate- what we'd collectively call "detritus."

Oh, my God. NOT DETRITUS! Here we go again...

So think about it for a second before you go all berserk:

Is "detritus", or other finely processed organic material the "doomsday machine" that many "experts" have long predicted will destroy your aquarium?

I don't think so.

I know-we all know- that uneaten food and fish poop, accumulating in a closed system can be problematic if overall husbandry issues are not attended to. I know that it can decompose, overwhelm the biological filtration capacity of the tank if left unchecked. And that can lead to a smelly, dirty-looking system with diminished water quality. I know that. You know that. In fact, pretty much everyone in the hobby knows that.

Yet, we've sort of heaped detritus into this "catch-all" descriptor which has an overall "bad" connotation to it. Like, anything which is allowed to break down in the tank and accumulate is "bad."

We're not talking about a substrate composed entirely of uneaten food and fish poop here. That's a different issue and a different problem. Now, I agree, it requires a lot of understanding and a real mental shift to embrace the idea of loving detritus in your tank.

The definition as accepted in the aquarium hobby is admittedly kind of sketchy in this regard; not flattering, at the very least:

"detritus is dead particulate organic matter. It typically includes the bodies or fragments of dead organisms, as well as fecal material. Detritus is typically colonized by communities of microorganisms which act to decompose or remineralize the material." (Source: The Aquarium Wiki)

That being said, everyone thinks that it is so bad.

I'm just not buying it.

Why is this necessarily a "bad" thing?

It's not.

In Nature, the leaf litter "community" of fishes, insects, fungi, and microorganisms is really important to the overall tropical environment, as it assimilates terrestrial material into the aquatic system, produces and consumes detritus, and acts to reduce the loss of nutrients to the forest which would inevitably occur if all the material which fell into the streams was washed downstream!

The key point: These materials and their resulting detritus foster the development of life forms which process these materials. Stuff is being used by life forms.

It goes without saying that the same processes which occur in Nature occur in our tanks- if we let them.

And botanical materials not only provide a "substrate" upon which these organisms can grow and multiply- they provide a sort of "on board nutrient processing center" within the aquarium. In my experience, based on literally a lifetime of playing with all sorts of combinations of materials in my aquariums' substrates ('cause I've always been into that weird shit!), I cannot attribute a single environmental lapse, let alone, a "tank crash", as a result of such additions or their resulting breakdown in otherwise well-managed aquairums.

I am of the opinion that a botanical-style aquarium, complete with its decomposing leaves and seed pods, can serve as a sort of "buffet" for many fishes- even those who's primary food sources are known to be things like insects and worms and such. Detritus and the organisms within it can provide an excellent supplemental food source for our fishes!

They give our fishes "options" to supplement their diets!

It's well known that in many wild habitats, like inundated forests, etc., fishes will adjust their feeding strategies to utilize the available food sources at different times of the year, such as the "dry season", etc. And it's also known that many fish fry feed actively on bacteria and fungi in these habitats...so I suggest once again that a blackwater/botanical-style aquarium could be an excellent sort of "nursery" for many fish species!

You'll often hear the term "periphyton" mentioned in a similar context, and I think that, for our purposes, we can essentially consider it in the same manner as we do "epiphytic matter." Periphyton is essentially a "catch all" term for a mixture of cyanobacteria, algae, various microbes, and of course- detritus, which is found attached or in extremely close proximity to various submerged surfaces. Again, fishes will graze on this stuff constantly.

Of course, anyone who keeps a planted aquarium could attest to that, right?

I firmly believe that the idea of embracing the construction (or nurturing) of a "food web" within our aquariums goes hand-in-hand with the concept of the botanical-style, blackwater (and brackish!) aquarium. With the abundance of leaves and other botanical materials now available to "fuel" the fungal and microbial growth, and the diligent husbandry and intellectual curiosity of the typical "tinter" (that's YOU!), the practical execution of such a concept is not too difficult to create, understand...and embrace!

We are truly positioned well to explore and further develop the concept of a "food web" in our own systems, and the potential benefits are enticing!

Appetizing?

We think so!

Stay curious. Stay resourceful. Stay excited. Stay creative...

And Stay Wet.

Scott Fellman

Tannin Aquatics