Blue whale catfish (Cetopsis coecutiens) care guide

Group
Freshwater fish
Other names
Whale catfish, Baby whale catfish, Blue shark catfish, Blue torpedo catfish
Family
Cetopsidae (whale catfishes)
Origin
South America: the Amazon, Tocantins and Orinoco basins.
Water
freshwater
Maximum size
26.5 cm
Temperature
22–26°C
pH
6–7.4
Hardness
3–18 dGH (estimated)
Minimum tank
600 litres
Care level
expert
Temperament
aggressive

Care

A smooth, whale-shaped, open-water catfish that is common in the wild but rarely seen in the trade. It swims constantly in midwater and needs lots of space, strong current and plenty of oxygen. PlanetCatfish gives no tank size; we estimate at least about 600 litres (a tank around 180 cm long) for adults. Keep the tank sparse and dimly lit with little décor and a soft substrate of sand or rounded gravel, leaving plenty of free swimming room. Water at 22–26 °C and pH 6–7.4 suits it. PlanetCatfish recommends weekly 25% water changes; good filtration and strong water movement are essential. Behaviour: this is not a fish to trust with others. In the wild whale catfishes bite chunks out of larger fish and eat smaller ones, and aquarium fish behave the same way. It may live in groups in nature, but there is little aquarium experience of keeping it in numbers. Sexing: males are slimmer and their dorsal fin tapers to a fine point when mature; females are stockier. It is listed as Least Concern on the IUCN Red List (assessed 2020). Sources: PlanetCatfish (planetcatfish.com/common/species.php?speciesid=339). Checked October 2026.

Diet

A predator and scavenger. In the aquarium it takes frozen and live foods; chopped mussel and live earthworms are favourites. Do not use feeder fish. Try to get it onto sinking tablets and pellets early. Take care not to overfeed, as it gorges.

Breeding

Not reported in the aquarium.

Compatibility and tank mates

Best kept on its own or with other whale catfishes in a species tank. It eats small fish and bites pieces out of larger ones, so most tankmates are at risk.

Last updated 5 October 2026. Community-edited care guide on Aquatic-Auctions.

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