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Issue: September 2012

Feeding Green: A Concept for All Catfishes (Full Article)

Author: Lee Finley

FINL T 0912
Photographer: Canoneer/Shutterstock
It should come as no surprise that catfish feeding strategies are as diverse as the species themselves. A recognized catfish expert explains why all catfish still benefit from some greens in their diet and offers advice on how to get them to eat them.

The time does fly. It seems only a short time ago that I was sitting at the same desk writing an article for the 50th anniversary issue of this magazine. Now the 60th anniversary has arrived. Ten years ago, I presented an overview of 50 years of the magazine. Although a lot has happened with the magazine over the past 10 years, it felt best to take a different tack this time around. So to this end, I am presenting a combination of two of my favorite topics: catfishes and their aquarium feeding.

The feeding of aquarium catfishes, or all fishes for that matter, has in many ways changed immensely since this magazine first debuted in late 1952. Commercial fish food formulas have gone through a lot of improvement, and these have benefited both keeper and pet. But what goes around also comes around, and many hobbyists are rediscovering some of the good parts of fish feeding from the 1950s and forward (more live foods, custom-blended homemade fish foods, etc.). This is not to say that many, if not most, of the—how shall I put this—more mature fishkeepers ever stopped their "older" ways. They continued along with these and have adopted (and adapted to) some of the newer aspects of the feeding of their charges.

Plecos and Other Veggie-Eating Catfish

For quite a few years, loricariids have been at the zenith of their popularity, and it only seems to keep peaking. For many years (decades, actually), they were basically the clean-up crew and were seemingly tolerated because of their algae-eating habits. Their detritus-eating character (utilizing for food much of that gunk [mulm] that can accumulate on the bottom of a tank that receives less than favorable maintenance) was also appreciated. But there was always a small group of aquarists who appreciated them more for what they were than for what they did.

Times have changed; loricariids are now one of the hottest groups of catfishes going and are appreciated by both dedicated catfish fans and general aquarists alike. Gee, do you think that the zebra pleco (Hypancistrus zebra) and the constantly growing list of similarly beautiful catfishes have had something to do with this?

A Varied Palate

First it must be noted that not all loricariids are primarily vegetal-feeding catfishes. The aforementioned H. zebra has shown itself, in the wild and captivity, to have a predilection for meatier foods. Although algae and detritus are eaten in the wild, this species also feeds on bryozoans (moss animals), non-shrimp crustaceans, and insect larvae (bloodworms).

Other loricariids also show a more carnivorous diet: Scobinancistrus spp., at least in the minimal literature available, are apparently totally carnivorous, although their main prey (bivalve mollusks and possibly snails) would provide some green material that they had ingested to the nutritional profile of these species.

Other loricariids, such as some Loricaria spp. and some other genera will, at least seasonally (or based on food in the environment), also feed heavily on meaty foods, such as various insect larvae, mollusks, and sponges. This situation needs to be kept in mind and researched when you might be considering picking up a new species from this large family of catfishes.

Commercial Diets

Loricariids adapt very well to commercial captive diets overall, and generally these should consist of foods with a higher percentage of vegetal material. Such foods also provide animal-based material to round out the nutritional profile. Most commercial foods tend to utilize Spirulina as their primary vegetal base. This is actually a cyanobacteria, but that is a tale for another time. Nonetheless, it is a wonderfully healthy food source for both fish and man. Although the name Spirulina is generally used, the most commonly farmed species belong to the genus Arthrospira. But the name Spirulina persists in general use and will probably do so for some time to come. There is also some increased use of Chlorella algae (a single-celled microalgae), which is a promising development.

Additionally, some formulas are utilizing various vegetables that you might expect to find at your dinner table. At least a couple of such foods are noted to contain (in addition to Spirulina) the following ingredients: carrots, celery, beets, parsley, lettuce, and spinach. Wow! Sounds like my supper. Of course, these foods have many additional elements, including vitamins and minerals, to round out their nutritional profile. Many of these commercial foods will be found in various formats—flakes, discs, sticks—so you can choose whichever fits the needs of your particular catfishes.

Algae

But, in using the above items, don't overlook the use of the real things. The first to be considered is algae. As noted above, algae is a major food item for many loricariids. Providing living algae for these catfishes is a goal to strive for; it gives the fish a more natural experience in that they can graze the food as they would normally do in the wild. But as anyone who has kept even a single bushy nose pleco(Ancistrus spp.) can attest, these fishes are very determined. Little natural algae growing in the tank will remain.

The best way to remedy this is to grow algae elsewhere and move it into the tank containing target species. This can be done by the feeding platform method. You take a suitable platform (a rock, piece of driftwood, flowerpot, etc.) and, in the absence of any fishes that will feed on algae, let it develop some nice green growth. This platform can then be moved to a tank containing your loricariid(s), and they will be supplied with a living green treat. Such platforms can be moved from other aquaria that might be growing algae. Such a tank could even be set up for this specific purpose, with numerous platforms that can be used on a rotating basis. But be sure that there are no health problems with any contained fishes that might potentially be transported along with them.

This can also be done outside (at least for warmer times of the year in more northern latitudes). I use Styrofoam fish boxes filled with multiple platforms making sure that they get full sun. Although algae will just grow there, I usually inoculate such containers with an initial algae dose from a tank, or tanks, in the fishroom. Such a set up of two or three boxes can provide a large amount of living algae as food. I will note my wife, Aline, was less than amused with such use of our patio, but she finally warmed up to it. Should you want to be specific with your algae type (e.g., Chlorella), you can purchase starter culture units, although these will end up having to compete with Mother Nature's choice of greens.

Vegetables

The feeding of real vegetables, as noted in some commercial foods above, is a tried-and-true method of providing green food to loricariids, and many other catfishes for that matter. There are numerous veggies that make an excellent and appreciated food source. This is an area wherein you can experiment to find your catfishes’ tastes.

A good place to start is with zucchini (or other squashes). These can be washed and then sliced (long- or cross-way, your choice) and offered to the fish. There are varying opinions as to whether such food should be served raw or lightly cooked (for about a minute or so in boiling water). I prefer the cooked method. First, such produce sinks easily and doesn't have to be tied down. Second, research has shown that lightly cooking zucchini makes more nutrients available by starting the breakdown of cellular walls. Note: With zucchini, make sure that your catfishes eat the skin—this is where the majority of the vitamin A is located. Sometimes this takes a bit of training because the softer middle will often be eaten and then the fish moves on. If you leave the skins in the tank and hold off on other foods a bit, they will take to it. Also, if you use across-cut rounds, slice the skin in one place so that you are not left with a skin ring. These can be a problem, and I have seen loricariids become entangled in them and die.

From zucchini, let your imagination run wild and try a variety of veggies. The FDA publishes nutritional charts for vegetables, and these can be a good guide to help you choose a good mix. Among others, I really like canned (or frozen) green beans. I most often have used French-cut style as a constantly present food for baby loricariids. The French style is good in that it exposes large areas of the softer pulp on which the young fishes initially feed.

Whichever way you go with veggies, and if you do your own light cooking, you can take the end product, freeze it on cookie sheets, and then store it in the freezer in air-tight containers. Then you just take out what you need and add to the tank(s).

Meaty Supplements

As a last thought, it should be noted that even the most algae eating of grazing loricariids do regularly ingest smaller quantities of meaty foods as part of the process. This may include insect larvae, small crustaceans, etc. So in addition to regular commercial-style foods, algae, and vegetables, do, in small quantities, regularly add foods such as frozen or freeze-dried brine shrimp, bloodworms, small krill, etc. for that extra flavor and nutritional punch. You can offer it right alongside the other foods or as a separate treat.

Other Herbivorous Cats

Three genera of the African catfish family Mochokidae (Atopochilus, Euchilichthys, and Atopodontis—the latter has never been imported, as far as I know) mentioned are basically ecological equivalents of many of the loricariids and enjoy a similar diet. Even visually there is at least enough of a resemblance that sometimes they have been sold as "African plecos," a name that I distinctly dislike, but that is another story for another time.

Predatory Catfishes

There are many aquarium-popular catfishes that are generally considered as a fish-eating group, but it can be taken beyond this in general principle. This diet grouping is not necessarily correct, as other foods such as shrimp, crabs, mollusks, etc. may also be eaten depending on the environment and/or time of the year. Many such predatory catfishes are also known to eat various fruits, again depending on the seasonal availability. The South American redtail catfish (Phractocephalus hemioliopterus) is such an animal, and its diet of such items has been well documented. Such work has also shown them to pass the seeds of such fruits, which then germinate and grow under proper conditions.

Even catfishes that may not specifically eat fruits do often ingest vegetal material in other ways. One way is that when prey items are digested, the contents of their gut then become food for the fish that ate them. At least some of the various prey fishes for a wide variety of predators are known to be vegetarians or detritus eaters. Detritus is broken-down vegetal material, generally with a good complement of micro and macro invertebrates. It has also been noted that predatory fishes may secondarily ingest some vegetal material when they are chasing and capturing their prey. This is no doubt true, but in some cases there may be more to the situation.

A case in point to the last situation is one of my favorite smaller (max size around 10 inches TL) predatory catfish, the auchenipterid Ageneiosus magoi. Two diet studies on this species do show it to be primarily a meat eater with fishes, frogs (in breeding season), shrimp, and insect larvae making up the bulk of its diet. But these two studies did show vegetal material (plants and detritus) present at respective values of 1) approximately 1.4 percent by weight and 2) 8.6 percent by occurrence. These figures don't, and really couldn't, show the additional vegetal percent comprised by the gut contents of their prey.

In any case, I was walking around the fish room one day, passing out small pieces of lightly boiled zucchini to a variety of tanks. As I went by the Ageneiosus tank, which contained six individuals around 5 to 6 inches long, I said “what the heck” and tossed in a couple of pieces. These were gobbled up as fast as something more meaty (bloodworms, guppies) would have been. More was added, more was eaten—and I know that the fish were not nutritionally deprived. The vegetal food then became, in small amounts, a regular part of their diet. Does this one example prove something? I think that it does, and it makes a point worth pondering and worthy of more experimentation with other catfishes.

So for any predatory catfishes that you might keep, do work on getting some vegetal material into their diet. Direct feeding of vegetables or fruits is ideal if possible, but if not, do feed them prepared foods (at least in part) with a good algal/vegetable formula. If you are a live-fish feeder, do use healthy fish and make sure to gutload them with a similar food before introducing them to the predator's tank.

Omnivores

Another group of predatory catfishes to be considered are the insectivore/mixed carnivore type. Actually, many of these might be more properly classified, for aquarium feeding purposes, as omnivores. This basically means that they take good amounts of meaty and vegetal foods. This includes many smaller and medium-sized catfishes that make their living by feeding primarily on insect larvae and pupae. Such a diet may also include terrestrial insects that unluckily fall into the water and other small meaty foods such as crustaceans, mollusks, etc.

Many of such catfishes may be deemed speculators in that they swim around “looking” for (by vision and tactile methods) and selectively take in promising foods. Such catfishes include many smaller pimelodids, doradids, and Corydoras and Synodontis species. This, as with the larger catfishes noted above, is often accompanied with the ingestion of some plant material (higher plants and/or detritus). This can often, at least seasonally, make up a pretty good part of the diet.

And their prey items are often life forms that make their living feeding on vegetation-sourced foods. Again, this is another good, and necessary, reason to make sure that this group of catfishes gets some green foods added to their diet. Many of these will take small amounts of regular vegetables but will do equally well on some of the available prepared foods (flakes, discs, sticks) that have a decent vegetal content. Just remember, pleco foods aren't just for plecos! They are an excellent addition to the diet of any catfish that will eat them—and that includes just about all of them.

These catfishes also appreciate live foods as part of their diet, and these can often be gutloaded with a number of vegetal-based foods. An outstanding guide to managing this feeding situation is the book Culturing Live Foods by Michael R. Hellweg (T.F.H. Publications, 2008). All aquarists should seriously consider having this book in their aquatic library.

Additional Considerations

As a final note, there are some topics that must be passed on, such as an initially planned discussion on the growing use of duckweed as an important fish food. But that’s for another time, and we will take it from there. Think green, feed green, and eat green.



See the full article on TFH Digital http://www.tfhdigital.com/tfh/201209#pg63

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