December 24, 2021

The meal plan...

One of the things that I enjoy most about the botanical method aquarium is that it can function much like the wild habitats it's intended to represent. And part of that function involves eco diversity and the production of life forms which serve as food for our fishes. The ability for fishes to at least supplement the diets that we provide them with by foraging in their aquarium is a big deal!

And yeah, we've talked about it a lot over the years here- because it IS a big deal.

Now, at least upon superficial examination, our aquarium leaf litter/botanical beds seem to function much like their wild counterparts, creating an extremely rich foraging area within our aquariums. And continuous reports form those of you who breed and rear fishes in your botanical-stocked aquariums indicate that you're seeing better acclimation for wild species, great color, more regularity and productivity in spawns, and higher survival rates of fry of some species than you've previously experienced.

It's not a coincidence. There is a great deal of merit to operating our aquariums this way. Nature provides all of the examples that we need.

As we've discussed before in this blog, the leaf litter beds 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.

By researching, developing, and managing our own botanically-infleunced aquaria, particularly those with leaf litter beds, we may be on the cusp of finding new ways to create "nurseries" for the rearing of many fishes!

The main sources of sustenance for fishes are the food webs, constructed by the flooded forests, aquatic herbaceous vegetation, and algae. Allochthonous sources (remember that term?) such as detritus and botanical materials (eg. leaves) are the main pathways for energy and nutrients provided by the forests to the aquatic habitats.

Phytoplankton in these so-called "impoverished" blackwater environments is something that we've likely downplayed!

In the rainy season, the main flow of what ecologists call "biomass" into the food web comes from the surrounding forests. Also, studies have found that, in the backwaters of the main tributaries, the floating submerged leaves of marginal vegetation are colonized by dense aggregations of epiphytes.

"Floating submerged leaves..."

Just think about that for a few minutes...

Interestingly, both algae and macrophytes -aquatic plants which grow in and around the water (emerged, submerged, floating, etc.) enter into aquatic food webs mostly in form of detritus (fine and coarse particulate organic matter) or being transported by water flow and settling onto the substrate.

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!).

Perhaps most interesting to us botanical-method aquarium people are epiphytes. These are organisms which grow on the surface of plants or other substrates (like botanicals and leaves!) and derive their nutrients from the surrounding environment. Fungal growths and biofilms are two such examples.

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.

I believe 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. Gut-content analysis of many fishes in the wild confirms this. Detritus and the organisms within the aquarium can provide an excellent supplemental food source for our fishes!

In the case of wild aquatic habitats, 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 animals use leaves and tree branches for shelter and not directly as a food item, grazing on this epiphytic growth is very important.

Natural habitats are absolutely filled with this stuff...in every nook and cranny. It's like the whole game here- an explosion of life-giving materials, free for the taking...

A true gift from Nature.

And it's all there for the taking (if you're a fish, that is) in a botanical-method aquarium filled with leaves and seed pods and such. The key, as always, is not to go crazy siphoning out every bit of detritus, and removing all of the fungal strands and biofilms from your wood, seed pods, and leaves. As we've mentioned many times, when we do this, we're essentially disrupting the food web in a very real way.

The key, like so many things we ask you to do in the botanical method aquarium approach- is to think a bit differently. Once you realize that that stringy-looking fungal growth is actually part of the food chain, things start getting quite interesting!

Many fishes will consume these items as a part of their daily "grazing" activities. Now, our aquarium fishes get a bit spoiled, especially after being with us for a while and knowing that they're never more than a few hours away from stuff like brine shrimp and black worms, etc. However, I can't help but imagine if there is some value to abstaining from feeding them prepared foods say, once a week, to let them sort of engage in their natural, instinctive feeding habits, like picking at the substrate, etc. In a botanical-method aquarium, this type of "feeding abstinence" could easily be achieved, right?

And then there is the food which comes from outside of the aquatic environment.

Many fish species take food from what are known as "allochthonous sources" (i.e. food originated from sources outside the aquatic habitat), such as insects, other invertebrates, and plant parts that fall from the nearby trees. Like, ever see videos of Pacus chowing on fruits that fall in the water? I've even seen pics of Arowanna leaping out of the water to pluck a frog off of a branch! And then, of course, there are terrestrial insects, which form a large part of the diet of many fishes.

Yeah, terrestrial insects are a very important and significant part of the diet of some small characins. In fact, a study of some Hemmigramus species indicated that a whopping 96% of their stomach contents were terrestrial insects, mainly...ants! This is actually not surprising, when you think about it, because ants are ridiculously abundant in tropical forests, and in particular in the central Amazon basin, where scientific surveys have estimated that they may constitute as much as three-quarters of the biomass of the soil fauna!

In addition to providing a potentially rich source of energy for Characins, ants tend to become vulnerable to predation once in the water, so they are "easy pickings" for tetras! The predominance of ants in the gut content analysis of Hemmigramus, Hypessobrycon, and other tetras may also indicate that these species feed naturally on the surface of the water, given that these insects tend to float and flail away on the surface after falling into the water.

The "allochthonous inputs" of tropical streams are really fascinating to me, for the reason that these are some of the easiest food items in many fishes's diets for us to replicate as naturally as possible. We've discussed before that items like Blood Worms represent an excellent, highly "realistic" representation of the insect larvae that fishes from these habitats consume.

Since items like ants and various flies are such an important component of the diet of many fishes, including things like fruit flies, small houseflies, and the aforementioned small ants in your fishes' diets is actually a really realistic representation of part of what they consume in the wild!

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.

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-method, 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 fish geek (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 almost beyond measure!

And further, I think that studying gut content analysis of the fishes we love is a very interesting way to develop more natural diets and feeding strategies for our fishes. You can find these gut content analysis studies by going deep on resources like Google Scholar, Scielo, etc. SO much good information there to glean!

Our "meal plan" should be more thoughtful than just purchasing a package of premium dried food. I mean, the dried foods today are amazing, and I'd be insane if I didn't urge you to get some Fluval "Bug Bites" to feed your fishes- it's literally made from insects! And, if your a bit more of a "DIY type"- the Rapashy line of gel premix foods- particularly the one called "Igapo Explorer"- are fantastic. Yeah, there are great prepared foods on the market today.

However, I encourage- actually urge- you to explore the idea of letting your aquarium do some of the work when it cones to feeding your fishes. To become more involved in studying how this works. It's pretty amazing stuff!

And of course, if you observe the behavior of many of your fishes in the aquarium, such as characins, cyprinids, Loricariids, 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 method aquarium, this is a pretty common occurrence, and I believe an important benefit of this type of system.

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 we have had in mind in years past, it is a beautiful thing to our fishes!

You can do this.

And, as a lover of the botanical-method aquarium approach, you're at the forefront of the art and science of creating functional food webs within the aquarium. And it all starts with a little research.

Stay curious. Stay engaged. Stay observant. Stay diligent...

And Stay Wet.

Scott Fellman

Tannin Aquatics