Phractocephalus hemioliopterus – Redtail Catfish

Phractocephalus hemioliopterus – Redtail Catfish is a species that should not be kept in an aquarium. They are beautiful fish, but they quickly become too big!

Phractocephalus hemioliopterus – Redtail Catfish

Phractocephalus hemioliopterus or Redtail Catfish was described in 1801 by Bloch & Schneider. Phractocephalus means: with protected head.

They belong to the family Pimelodidae or the Long-whiskered Catfishes,. This family includes some 32 genera and 113 species. The genus Phractocephalus is home to only one species: Phractocephalus hemioliopterus.

In the past, this species of fish was mainly kept in very large aquariums in zoos. Unfortunately, they have also been for sale in regular pet stores for a few years now. Due to their size, they are NOT suitable for most aquariums.


This large catfish is very recognizable by its red tail. The top of the body is grey/brown with small spots, the underside of the body is white. The dorsal fin has a large white band. Around the very large mouth are the antennas with which they can scan the environment in the dark. The males and females are indistinguishable from each other. You cannot confuse this species with any other species, there are no similar species.

A fully grown Redtail Catfish can reach a length of about 180 centimeters in the wild. With a maximum weight of about 80 kilograms, it is a seriously large fish.


Despite its size, Phractocephalus hemioliopterus is actually a fairly peaceful species. Obviously, they will eat anything that fits their very large mouth, but they just ignore larger species. Make no mistake with the size of their mouth, they can handle larger fish than you would think at first glance.

They can be territorial towards conspecifics or other catfish, especially in an aquarium that is actually too small. With a sufficiently large aquarium, you do not have this problem.


This species has a very large distribution area in South America. They live in the Amazon basin, Rio Orinoco and Rio Marañón where they occur in fast-flowing waters to the stagnant waters of flooded forests. Around these rivers, Redtail Catfish occur in Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru and Venezuela.

In the wild, it is an omnivore. Everything that comes before his mouth and fits in is eaten. They mainly eat fish, invertebrates and fruit that has fallen into the water.


In the aquarium, the Redtail Catfish will accept all the food it is presented with. You can feed them meaty foods such as live or dead fish, shrimp, mussels, smelt, worms, etc. This species grows very quickly, especially in an aquarium where they often get too much food. Young specimens really only need to be fed every other day. As they get older you can reduce the number of feedings, feed adults only once a week. You can tell by the behavior of the fish when it is time to feed. Once fed, they become lethargic and often remain on the bottom. If they are permanently swimming around they are hungry and you could feed them.

The leading cause of death in Phractocephalus hemioliopterus is overfeeding! Also, do not give them beef heart or chicken, the catfish’s stomach cannot digest this properly and causes excess fat to build up in the fish. Feeder fish such as goldfish are also not recommended unless you breed them yourself. These feeder fish usually come from the wholesaler and can cause diseases. The Redtail Catfish is not immune to this!

The Aquarium

Even a very large aquarium can’t really give these fish the space they need. If you still want to keep them, think of a minimum aquarium size of 4 meters wide, 2.5 meters deep and 1.20 meters high. In principle, this species does not require any decoration. If you want to decorate the aquarium anyway, it’s only for yourself, the fish don’t care. Make sure that any decoration is too heavy to be moved, because of its size, this fish will otherwise completely rebuild the aquarium.

The bottom may remain completely bare. You can choose to cover the bottom with sand or with large pebbles, this will be moved regularly by the Redtail Catfish. Aquarium gravel is not recommended because it can get stuck in the gills. Phractocephalus hemioliopterus has a tendency to swallow anything that fits in its mouth. So make sure that all aquarium equipment is kept outside the aquarium to prevent them from swallowing heating, filter outlet etc. This also applies to any aquarium decoration.

The lighting must be somewhat dimmed, the fish feel more at ease in dimmed light. Filter the aquarium with a generously sized external biological filter. Fish of this size produce lots of waste!

For young/small specimens it is advisable to place some large pieces of driftwood where they can hide behind/under.

Breeding Redtail Catfish

Breeding this beautiful fish species is not feasible within the modest dimensions of an aquarium. Commercial farms in Asia breed the Redtail Catfish on a large scale, mainly for consumption. Due to its very fast growth and large dimensions, it is very suitable for this.


Phractocephalus hemioliopterus is a species of fish that shows a beautiful drawing at a young age and as an adult. Unfortunately, this species grows too large to keep in a regular aquarium. Even though the sellers in the store say they won’t get that big, please don’t buy them. Zoos no longer accept animals that have outgrown the aquarist, there are simply too many of them. Fish DO NOT stay small when kept in a small aquarium! Redtail Catfish eventually grow to around 180 centimeters in length and can weigh up to 80 kilos!!!


Not everyone wants to see this video but it will give you an idea of how large the Redtail Catfish can get:


John de Lange

Copyright images

Ron DeCloux
Yu-Chia Chang

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