Cetopsis coecutiens

Blue Whale Catfish

Classification

Cetopsidae. Subfamily: Cetopsinae

Distribution

Has a widespread natural range, inhabiting areas of Venezuela, Colombia, Ecuador, Peru, Brazil and Bolivia. It’s found in the Amazon, Tocantins, and Orinoco River basins.

Habitat

Predominantly swims in open water in large, flowing rivers.

Maximum Standard Length

10.6″ (26.5cm).

Aquarium SizeTop ↑

An active species that needs a tank measuring at least 48″ x 18″ x 18″ (120cm x 45cm x 45cm) – 255 litres when fully grown.

Maintenance

Decor isn’t particularly critical but water movement is. It does best with a good degree of flow running through the tank. Try to position the filter return so that it breaks the surface. The agitation created by this will provide the desired levels of dissolved oxygen. Alternatively, position a powerhead at one end of the tank. Dim lighting is also preferable, as its natural waters are usually quite deep and murky. It is much more active under these conditions.

Water Conditions

Temperature: 72-79°F (22-26°C)

pH: 6.0-7.4

Hardness: 2-15°H

Diet

There’s no need to provide live fish, as it is an eager and aggressive feeder. Offer a meaty diet of frozen and live foods such as prawns, mussel, cockle, lancefish, earthworms etc. Some specimens will even accept dried foods. It is so greedy that overfeeding comes very easily.

Behaviour and CompatibilityTop ↑

Best kept alone, as not only will it eat smaller tankmates, it will often bite chunks out of larger fish as well. In nature, it has been seen ripping pieces of flesh from much bigger fish than itself. Some success has been had with keeping it in groups, as it seems less likely to regard conspecifics as a source of food.

Sexual Dimorphism

Females are fuller-bodied than males, and males develop a pointed dorsal fin as they mature.

Reproduction

Unknown. Certainly not achieved in the hobby to date.

NotesTop ↑

An infrequently seen but very interesting oddball species for those who are looking for something a little different. To others, it might appear to be a rather nasty species. In the wild, it swims in voracious feeding groups. Apparently, it can home in on weakened or distressed fish as it has a very well developed sense of smell. Other specialisations include the tiny eyes and particularly slimy skin. The former are reduced in size and covered by a thin layer of skin so they are less likely to be damaged when it is burrowing into prey, while the latter makes it easier for it to enter. Seeing a group of these in a feeding frenzy in the aquarium is quite something. It could definitely inflict a nasty bite, so exercise due caution when performing tank maintenance.