The Helicopter catfish, Wallago attu, weighs as much as seven Jack Russell terriers or 45,000 Neon tetras when it's fully grown, says Matt Clarke.
Common name: Helicopter catfish
Scientific name: Wallago attu
Origin: Widespread across most of tropical Asia. Museum specimens have been recorded from Cambodia, Bangladesh, India, China, Myanmar, Pakistan, Nepal, Indonesia, Syria, Thailand, Vietnam and Afghanistan.
Size: Humungous! Wild fish can reach over 2m/6'6" and over 45kg/100lbs in weight - that's equivalent to seven Jack Russell terriers or 45,000 Neon tetras!
Diet: Stomach analyses of wild fish show youngsters favour crustaceans, molluscs, insects and small fish. Adults feed predominantly on cyprinids, but will probably take anything that can fit in their capacious and toothy mouths. Trout segments are probably ideal for larger specimens. There is no advantage in offering live foods.
Water: Very widespread, so probably very adaptable to different chemistries and even to relatively low, slightly sub-tropical temps.
Habitat: Lives in deep, slow- moving rivers among the silt as well as in deeper pools in main rivers.
Aquarium: Enormous. A mature adult needs a huge tank, plus a massive filter system and lots of large, regular water changes. They're best kept alone, and only by those experienced in keeping very large fish.
Notes: The mouth is filled with sharp, backward-pointing conical teeth for holding onto fish. It can seriously wound you. It's a popular game fish in Asia and bites aggressively when removed from the water. We cannot be held responsible for the loss of limbs...
Similar species: There are three others in the genus including leerii, hexanema, and maculatus. Several others have been split from the genus. W. leerii has also been imported into the UK recently - it also reaches over a metre. W. hexanema and maculatus are rarer.
Identification: Wallago can be distinguished from most other Asian silurids by their characteristic mouths. The gape is very wide and (usually) extends past the eye posteriorly. In most other silurids, the mouth stops before the eye. W. attu has five dorsal rays, 77-97 soft anal rays (if you can count them!) and two pairs of barbels.
Breeding: Believe it or not, it's been bred in captivity, albeit in earth ponds in Asia. Said to migrate to grasslands when the rivers flood, and spawns at the water surface. Becomes sexually mature at 2kg.
Availability: Rarely on sale. This one was at Wharf Aquatics in Notts, whose staff are experienced with large species like this one.
Price: Just 29.95.
This article was first published in the October 2004 issue of Practical Fishkeeping magazine.