The "nutritional" dynamic of botanical-style aquariums...

The world of botanical-style aquariums is filled with new ideas, theories, and some occasional breakthroughs. Interestingly, one of the biggest "developments" in the botanical-style aquarium world is something which has been with us- literally staring us in the face- for many decades; only recently gaining a bit more "traction" in our world as more and more hobbyists embark on this path:

The idea of the aquarium producing food sources for its inhabitants.

We've talked about this idea a lot over the past several years, and it's something that is getting more and more difficult to ignore. 

If you've followed us for any length of time, you're well aware that we are not just pushing you to play with natural, botanical-style aquariums only for the pretty aesthetics. I mean, yeah, they look awesome, but there is so much more to it than that. We are almost as obsessed with the function of these aquariums and the wild habitats which they attempt to represent!

And one of the most important functions of many botanically-influenced wild habitats is the support of food webs. As we've discussed before in this blog, the leaf litter zones in tropical waters are home to a remarkable diversity of life, ranging from microbial to fungal, as well as crustaceans and insects...oh, and fishes, too!  These life forms are the basis of complex and dynamic food webs, which are one key to the productivity of these habitats.

As a hardcore enthusiast of the botanical-style aquarium, you're more than well-attuned to the nuances involved in managing a system filled with decomposing leaves, seed pods, wood, etc. And you're keenly aware of many of the physiological/ecological benefits that have been attributed to the use of these materials in the aquarium.

However, I am willing to bet that many in the hobby have not really considered the "nutritional" aspects of both botanicals and the life forms they foster as an important part of the "functional/aesthetic" dynamic we've touched on before.


Like so many things we discuss here, it's important to look at the wild habitats from which our fishes come, and consider some of the types of food sources that our fishes might utilize in the wild habitats that we try so hard to replicate in our aquariums. We should have a greater appreciation for them when they appear in our tanks, IMHO. Perhaps we will even attempt to foster and utilize them to our fishes' benefits in unique ways? 


MACROPHYTES: One of the important food resources in natural aquatic systems are what are known as macrophytes- aquatic plants which grow in and around the water, emerged, submerged, floating, etc. Not only do macrophytes contribute to the physical structure and spatial organization of the water bodies they inhabit, they are primary contributors to the overall biological stability of the habitat, conditioning the physical parameters of the water. Of course, anyone who keeps a planted aquarium could attest to that, right? 

One of the interesting things about macrophytes is that, although there are a lot of fishes which feed directly upon them, the plants themselves are perhaps most valuable as a microhabitat for algae, zooplankton, and other organisms which fishes feed on. Small aquatic crustaceans seek out the shelter of plants for both the food resources they provide (i.e.; zooplankton, diatoms) and for protection from predators (yeah, the fishes!).

So, plants in the aquarium have been valued by aquarists "since the beginning" for all sorts of benefits- that's not really groundbreaking. And some fishes directly consume plants. I personally think that one of the more interesting functions of plants in the aquarium is to serve as this sort of "feeding ground" for fishes in all stages of their existence. Oh, yeah, they do look cool, too! So, perhaps just setting up an aquarium for the purpose of growing plants to feed fishes-in multiple "formats" is a good one.

Of course, this POV will pretty much get me trashed by most of my aquatic plant-loving friends: "WTF, Fellman- you're a savage! Are you suggesting to set up a planted aquarium to feed my fishes? Really?

Well yeah. sort of. Why not? Just think about it...


EPIPHYTES: Perhaps most interesting to us botanical-style aquarium people (and perhaps far more acceptable to our planted aquarium friends!) are epiphytes. These are organisms which grow on the surface of plants or other substrates and derive their nutrients from the surrounding environment. They are important in the nutrient cycling and uptake in both Nature and the aquarium, adding to the biodiversity, and serving as an important food source for many species of fishes.

In the case of the aquatic habitats we geek out over, like streams, ponds, and inundated forests, epiphytes are abundant, and many fishes will spend large amounts of time foraging the "biocover" on tree trunks, branches, leaves, and other botanical materials. Although most fishes use leaves and tree branches for shelter and not directly as a "food item", grazing on this epiphytic growth is very important.  


And many other creatures make use of these materials as well. Some organisms, such as nematodes and chironomids ("Bloodworms!") will dig into the leaf structures and feed on the tissues...and ultimately become food sources themselves for our fishes!

"Cycle of life" and all that, huh?

FUNGI: And, what discussion of epiphytes would be complete without mentioning our buddies, the aquatic hyphomycytes- or fungi as  they're better known! 

The “aquatic hyphomycetes” are specialists at breaking down stuff like leaf litter. Another group of specialists, "aero-aquatic hyphomycetes," colonize submerged plant detritus in stagnant and slow- flowing waters, like shallow ponds, puddles, and flooded forest areas. Fungal communities differ between various environments, such as streams, shallow lakes and wetlands, deep lakes, and other habitats such as salt lakes and estuaries. But they're pervasive in aquatic habitats. 

And we see them in our own tanks all the time, don't we?

Fungi tend to colonize wood because it offers them a lot of surface area to thrive and live out their life cycle. And cellulose, hemicellulose, and lignin- the major components of wood and botanical materials- are degraded by fungi which posses enzymes that can digest these materials! Fungi are regarded by biologists to be the dominant organisms associated with decaying leaves in streams, so this gives you some idea as to why we see them in our aquariums, right?

And of course, fishes and invertebrates which live amongst and feed directly upon the fungi and decomposing leaves and botanicals contribute to the breakdown of these materials as well! Aquatic fungi can break down the leaf matrix and make the energy available to feeding animals in these habitats.

And look at this little gem I found in my research:

"There is evidence that detritivores selectively feed on conditioned leaves, i.e. those previously colonized by fungi (Suberkropp, 1992; Graca, 1993). Fungi can alter the food quality and palatability of leaf detritus, aecting shredder growth rates. Animals that feed on a diet rich in fungi have higher growth rates and fecundity than those fed on poorly colonized leaves. Some shredders prefer to feed on leaves that are colonized by fungi, whereas others consume fungal mycelium selectively..."

"Conditioned" leaves, in this context, are those which have been previously colonized by fungi! They make the energy within the leaves and botanicals more available to higher organisms like fishes and invertebrates! 

It's easy to get scared shitless by this stuff-cause it looks pretty "contrary" to what we've been told is good to see in our aquariums...Yet surprisingly, it's even easier to exploit it as a food source for your animals! This is a HUGE point that we can't emphasize enough.

DETRITUS: The resulting detritus produced by the "processed" and decomposing plant matter is considered by many aquatic ecologists to be an extremely significant food source for many fishes, especially in areas such as Amazonia and Southeast Asia, where the detritus is considered an essential factor in the food webs of these habitats.

And of course, if you observe the behavior of many of your fishes in the aquarium, such as characins, cyprinids, Loricarids, and others, you'll see that in between feedings, they'll spend an awful lot of time picking at "stuff" on the bottom of the tank. In a botanical style aquarium, this is a pretty common occurrence, and I believe an important benefit of this type of system. 

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!

It's well known that in many 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 I suggest one again that a blackwater/botanical-style aquarium could be an excellent sort of "nursery" for many fish species! 

PERIPHYTON: 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.

And then, of course, there's the "allochthonous input" that we've talked about so much here: Foods from the surrounding environment, such as flowers, fruits, terrestrial insects, etc. These are extremely important foods for many fish species that live in these habitats. We mimic this process when we feed our fishes prepared foods, as stuff literally "rains from the sky!" Now, I think that what we feed to our fishes directly in this fashion is equally as important as how it's fed.

I'd like to see much more experimentation with cultivation of foods like ants, fruit flies, and other winged insects. Of course, I can hear the protests already: "Not in MY house, Fellman!" I get it. I mean, who wants a plague of winged insects getting loose in their suburban home because of some aquarium feeding experiment gone awry, right? This idea is the realm of bachelors/bachelorettes, anti-social types, and people with very understanding significant others!

That being said, I would encourage some experimentation with ants and the already fairly common wingless fruit flies. Can you imagine one day recommending an "Ant Farm" as a piece of essential aquarium food culturing equipment? Why not right? Sales of ant farms would spike and manufacturers would have no reason why. Yeah, executives at these companies would think that kids everywhere were falling in love with ants again, like they did in the 60's-when the reality is that us fish geeks would be using them as the terrestrial version of a brine shrimp hatchery...Oh, the horror!

"So, all this talk is great, but how do we start "in tank culturing" of these supplemental food sources, Fellman?"


Just start a botanical-style aquarium. Nature will do the rest. Really. Especially if you don't try to "edit" the process...

As many of you may recall, I've sadistically enjoyed the desperate calls for help which many harder aquascaping enthusiasts express on forums when a new piece of driftwood is submerged in the aquarium, resulting in a big burst of fungi, algal growth and biofilm! Yeah, I realize this stuff looks pretty shitty to a lot of hobbyists, and I should be less gleeful about their plight...But some of these people are the same bastards who go on to become "high end aquascapers" who continually and unflinchingly trash our philosophies and methodology online, so... all's fair in love and war, right?

If they only knew the "gift" that these things are...

Yup. I think we need to let ourselves embrace this. I think that those of us who maintain blackwater. botanical-style aquariums have already made the "mental shift" to understand, accept, and even appreciate the appearance of this stuff. Perhaps other aquarists will eventually come around on this?

When you start seeing your fishes "graze" casually on the materials that pop up on your driftwood and botanicals, you start realizing that, although it might not look like the aesthetics that contest judges have in mind, it is a beautiful thing to our fishes!

And my ultimate guilt and sympathy towards the hapless aquascaping crowd makes me think that an "evolved" preparation technique for driftwood might be to "age" it in a large aquarium that also serves as an acclimation system for certain fishes. For example, fishes like Headstanders (Chilodus punctatus), Leporonus, Pencilfishes, and various loaches, catfishes, and barbs, would be excellent additions to this "driftwood prep tank." You could get the benefit of having the gunky stuff accumulate on the wood outside of your main display (if it bothers you, of course), while helping acclimate some cool fishes to captivity!

Just throwing the idea out there.

And of course, we've talked before about the "botanical nursery" concept- creating an aquarium for fish fry that has a large quantity of decomposing botanicals and leaves to foster the production of these materials, which serve as supplemental food for your fish fry. I have done this before myself and can attest to its viability. You fishes will have a constant supply of "natural" foods to supplement what you are feeding them in the early phases of their life. Learn to make peace with your detritus! 

And, for like the 20th time in "The Tint", I need to call your attention to my highly successful "leaf-litter-only" aquarium attempts. These simple to configure, yet ecologically complex tanks may be the ultimate expression of this "self generating food" concept. 

This little discussion has probably not created any earth-shattering "new" developments, but I believe that it has at least looked at a few of the terms you see bandied about now and again in hobby literature, perhaps clarifying their significance to us. And I think it's really about us understanding what happens in Nature and how we can work with it instead of against it, taking advantage of the food sources that She provides to our fishes when we don't rush off for the algae scraper and siphon hose before considering the upside!

These life forms are real gifts from Nature...And you can benefit from them simply by "working the web" of life which arises without our intervention as soon as leaves, wood, botanicals, and water mix-as they've done in Nature for eons.

Another "mental shift", I know...Yet, one which many of you have already made, no doubt, and many more will benefit from by making! I certainly look forward to seeing many examples of us utilizing "what we've got" to the advantage of our fishes! 

Stay thoughtful. Stay resourceful. Stay observant. Stay creative. Stay engaged.

And Stay Wet.


Scott Fellman

Tannin Aquatics 





Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

November 20, 2021

LOL, exactly! Nothing wrong with a good helping of “preconditioned leaves!”



November 18, 2021

Having been a mycelium enthusiast long before I ever had a planted tank, I’m not at all surprised that many fish prefer the conditioned leaves! After all, what’s a nice cup of tea if not conditioned leaf water?

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