Catfishes: A Chaotic Biodiversity that is still Waiting to be Discovered

Catfishes: A Chaotic Biodiversity that is still Waiting to be Discovered

Written by Andreas Iliopoulos Thursday, 07 February 2002 00:00

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All of us that are involved with fish keeping in captivity are fated to sooner or later handle Catfishes. There are two specific reasons for that, and acquiring catfishes for the first reason usually makes the hobbyist aware of the second.

We use several species of catfishes in our community tanks because these fishes do a lot of work in a closed ecosystem such as an aquarium, so they keep the biological chain in function.

Catfishes collect all the uneaten food from the substrate and consume it. They also play the role of the scavenger and keep our tanks clean of corpses and dead organic materials. Also, catfishes are the ones that maintain the quantity of algae in our tanks and ponds.

In both cases, these kinds of fishes are very important; as uneaten food that is decaying or an excess of algae in the enclosed fragile aquaria system would produce pollutants that would upset the desired balance.

So the first, and main, reason we keep them in our tanks is our need to control the food chain naturally. The second reason has to do with the strange beauty of these species and their odd behaviour. Their peculiarity, as well as their importance as animals, makes them a highly wanted addition to a hobbyists’ collection. The rarity of some species – even in their natural environment – and their vast biodiversity makes some aquarists dedicated in keeping only catfishes in their tanks, and some hobbyists develop a manic obsession with the biology of the species, constructing a second hobby within the hobby.

Some Useful Information about the Systematic Biology of Catfishes

Catfishes belong to the large group of Osteichthyidae, belonging to the class of Actinopterygii, which means that their skeletons are constructed by bones rather than cartilage or cartilaginous plates. Their fins are vermiculated, in contrast to the fleshy fins with bones that sharks, rays and primitive Coelacanthus and Coelacanth-like fossils have. They also belong to the order Siluriformes, which includes over thirty families and more than four hundred species that inhabit almost all the waters of our planet, as it is shown on Table 1.

Here we shall try to uncover as much information as we can about the most abundant families and species in the aquarium hobby. This does not mean that we should disregard the rest of the families and species (see Table 2 for a detailed classification that has been achieved until today; as every day new species are collected and the research goes on and on).

The most common species of catfishes that are usually seen in community tanks belong to the families Callichthyidae (eg Corydoras) and Loricariidae (eg Ancistrus).

In tanks that house members of the family Cichlidae from the east African rift lakes, we usually see catfishes that belong in the families Mochokidae (for instance, Synodontis species) and Bagridae (Auchenoglanis species). It is a bit uncommon, though, to find members of the Schilbeidae family in such tanks (due to the size of the most of these catfishes) with Victorian cichlids and even more uncommon to see members of the Malapteruridae, due to their large size and predatory habits (they electrocute their prey).

Very popular are some members of the Doradidae family (eg Acanthodoras), Pimelodidae family (such as Pimelodella pictus, P. maculatus, Phractocephalus hemiliopterus) from the South America region, Pangasiidae (Pangasius species) and Schilbelidae from Asia. Also, very rarely, we find African Schilbelidae (eg Schilbe intermedius).

Unfortunately, we often times see members of the Clariidae family (Clarias species) in unsuitable tanks. These species grow very large (Clarias batrachus - 50cm, C. gariepinnis - 75cm) and they are usually housed with unsuitable tank mates, on which they satisfy their voracious appetite. The ending is that in these tanks only the catfishes remain, as anything that fits in their mouth will be devoured after a while. Another oddity is that these fishes can breath atmospheric air, and they may live many hours out of water, achieving remarkable records if the humidity is enough for them. It is said that they are the last animals that die in African water pits during the dry season when the savannah becomes parched and kills crocodiles and hippos.

It is very rare to find members of the other families in tanks; their appearance is usually witnessed only in tanks of very dedicated aquarists.

Update: Wolfgang Ros sent us the following information: For current pictures and a short report of clarias batrachus - breeding / mating, please take a look here.  My detailed report "Erfolgreiche Froschwels-Nachzucht im Aquarium" (Succeeded walking catfish - mating in the tank) is published in: "Die Aquarien- und Terrarienzeitschrift" (DATZ) 7/04, pages 12-15. Unfortunately only the first section of this report is available on line here. Whoever feels this is of interest can order the DATZ 7/04 at the publishing house "ulmer" (for more information please contact This e-mail address is being protected from spambots. You need JavaScript enabled to view it ).

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