September 20, 2017

Functional aquascaping and the feeding habits of our fishes: A different direction?

We talk a lot about how to feed our fishes, and how best to provide nutrition for them. However, have you ever thought of how it might be possible to create an interesting fish community and display based on the different feeding strategies of fishes?

In other words, aquascaping your tank to support the various feeding adaptations of different fishes!

Hmm...ponder the possibilities here...

If you think about it, a typical tropical stream has a variety of different feeders. Many of our favorite fishes may be classified as "periphyton" grazers, which have small mouths, fleshy lips, and numerous tiny teeth for rasping. "Periphyton", by the way, is defined as "...freshwater organisms attached to or clinging to plants and other objects projecting above the bottom sediments." Ohh- sounds good to me! This stuff is abundant in all sorts of streams, but can be limited by availability of light and solid substrates.

For this reason, specialized grazing fishes are rather uncommon in streams that contain shifting sand substrates, especially where there is dense shading by overhanging trees and shrubs. In streams possessing muddy bottoms, there is typically not enough aquatic plant or woody materials present to support an extensive community of periphyton sufficient to support grazing fishes.

In these types of habitats, many grazing fishes feed on our old fave, detritus- and other sediments that are rich in organic matter, especially during various times of the year when the periphyton is more limited. Stuff like fungi and diatoms provide additional nutrition for fishes that graze, so our decomposing leaf litter and seed pods and such are useful for supporting this growth! It's noteworthy to point out that detritus is a less nutritious resource for grazers than the typical periphyton, especially for fishes like loricariid catfishes and such- and is thought by scientists to only be actively consumed when the periphyton growth is limited. So, interestingly, fishes do shift their feeding patterns to adapt to seasonal and other changes in their habitat..something we can replicate in our aquariums, no doubt!

As we've talked about previously, aquatic invertebrates and crustaceans are one of the primary foods consumed by many fishes which reside in tropical streams, and the amounts and types are dictated by the environment of the stream, which includes factors like the surrounding topography, current, elevation, surrounding plant growth, etc. Many fishes, like Headstanders and others, simply consume tiny crustaceans as part of their sediment feeding activity. Now, we're not likely to set up aquariums with fine, silty sediments stocked with tons of little copepods and worms and such...but if we were, I wonder how long it would take a few fishes to decimate the population. Is it possible to create a real "active substrate", filled with these creatures, and to be able to "pre-stock' it with tons of small life forms prior to the introduction of fish? Would there be some way to replenish the population of these creatures (and thus the substrate itself) periodically? An interesting experiment to think about, huh?

And then, there are those insects. You know, terrestrial ones, like ants, flies, spiders, etc. They're especially important to fishes which reside in streams in rain forests and other locales where the land and water interact extensively, like areas of riparium vegetation. Now, not everyone's cup of tea, I know, but could, for example, ants- which make up a surprisingly large part of the diet (based on gut content analysis) of some fishes like characins and even some cichlids in Amazon streams- be a practical supplement food for our fishes? I can just see a sudden surge in the popularity of "Ant Farms" as hobbyists race to culture their own populations of these insects!

In the forests of South America, Asia, and Africa, where streams run throughout the year, there are numerous "allochthonous resources" to be had, such as fruits, flowers, the aforementioned terrestrial insects, and seeds, which fall into the water and help comprise part of the diet of many fishes. Interestingly, it's thought that many of the fruit and seed-eating fishes (like Myleus, Metynnis, and other characins) don't actually destroy the seeds of fallen fruits when consuming them, and thus might actually be significant seed dispersal agent sfor riparian and floodplain trees in these areas! And, interestingly, lots of these fishes also consume insects and aquatic invertebrates, depending upon the season- a strategy which makes sense, as it takes advantage of "what's available" at different times of the year.

Now, there are a fair number of fishes that consume aquatic plants, or more properly- parts of aquatic plants- as part of their diet, such as Doradid catfishes and Anomostids. Often, they're also consuming epiphytic algae and such in the process. Now, I'm not suggesting to utilize plants in your aquascape for feeding purposes; however, it's not entirely out the the realm of reality to do this, right? Now, a lot of omnivorous fishes in the wild are removing the periphyton from the roots of floating plants in some streams, so it may make some sense to utilize these plants as sort of "for culture stations" in your aquascape to support the feeding habits of many fishes, such as characins, Danios, Barbs, etc.

It's interesting to contemplate designing a biotope or other aquarium around feeding, an important but often overlooked aspect of fish behavior (when it comes to tank design, that is! With a little research, planning, and a lot of experimentation, what interesting discoveries can be made? What breakthroughs await? Combining our much evolved expertise in fish feeding with our love of aquascaping seems almost a natural combination, doesn't it?

Stay creative. Stay curious. Stay studious. Stay innovative.

And Stay Wet.

Scott Fellman

Tannin Aquatics

Scott Fellman

Author

2 Responses

Scott Fellman

September 21, 2017

Good to hear of this experience, Garrett!

I think it’s that problem, as you’ve stated, of continuously replenishing the supply of living food organisms…trying to “stay out in front” of the fishes as they decimate the populations! Ive done stuff like this with reef tanks: “Pre-stocking” with food organisms, and than continually restocking throughout the tank’s functional lifetime. It’s possible, but requires a lot of effort! I do like the duckweed idea, myself (As a vegetarian myself, I’d ALSO pass on the “Duckweed Burger” concept, lol!

-Scott

Garrett

September 20, 2017

I’ve seen this happen with both plants and insects in my aquaria. I accidentally cultivated quite a healthy population of copeopods and worms in one of my first tanks. Then my platies reproduced, and while I had almost 100% fry survival, they pretty much wiped out the microfauna. However, once they grew older and I got rid of them, the bugs came back… I think that if you are able to start with a significant population of micro- and macro-fauna, you will see it blossom and shrink depending on the rest of the tank’s needs… just like in nature!

Of course, this depends on who’s in the tank. Yoyo loaches can completely eradicate snail populations in days (even the tenacious trumpet snails) and while I have only anecdotal evidence, I’m fairly certain that my kuhli loaches wiped out the hundreds of ramshorns in my one tank, either by consuming the snails or simply devouring their eggs and outlasting the adults.

The key may be in providing enough cover for the “food” organisms (difficult enough with the slippery kuhlis). I’ve begun experimenting with heavier layers of leaf litter, hoping that this will help both bugs and fish to thrive, acting as an in-tank “refugium”, although it’s too early in the game to tell whether this will work.

When it comes to plants, it helps to have large quantities of rapidly-reproducing ones. Hornwort has been a treat for some fish. Green algae, much-maligned by the aquatic community, is great for grazers. Duckweed is another good one – yes, it will cover your water surface, clog your filters, and not have exotic colours or shapes, but it’s also a great plant for blackwater, and a prime source of vegetable protein – so good, that in some parts of the world it is cultivated for human consumption! (As a vegetarian, I have yet to try a duckweed-burger though!) My Endlers and my paradise gourami will occasionally be seen snacking on the roots and leaves of this prolific plant.