The Sailfin tetra, Crenuchus spilurus, is becoming more common in the shops, says Matt Clarke.
Common name: Sailfin tetra
Scientific name: Crenuchus spilurus
Origin: Quite widespread and known from the Orinoco and Amazon
basins in Brazil, French Guina, Guyana, Suriname and Venezuela.
Size: About 5cm/2", but quite stocky.
Diet: A micropredator that feeds on small aquatic and terrestrial invertebrates in the wild. Aquarium specimens will take frozen bloodworm, brineshrimp and, after a while, flakes.
Aquarium: Very little is known about this unusual characin other than it is found in small streams and rivers. Unlike most tetras, this is quite an aggressive, non-gregarious species, so it's really something for the specialist. It's also got a big mouth and might be able to swallow very small fish.
A South American river biotope with a sandy substrate and plenty of bogwood should be fine. These fish are OK to mix with other larger peaceful fish, including small and medium-sized cichlids.
Sexing: The males are much larger and stockier than the females, and have longer fins and brighter markings.
Breeding: This species is unusual for a tetra since it deposits its eggs on a leaf, rock or piece of bogwood.
Notes: The fish get their name from the Greek 'krenouchos' - the god of running waters.
Similar species: This is a member of the Crenuchidae family and is in the crenuchine sub-family with two other species: Poecilocharax bovalii and P. weitzmanni. The latter is sometimes imported into the UK, bovalli is rarer.
Identification: This species is the only member of the Crenuchus genus and isn't likely to be confused with anything else.
Availability: These fish were spotted on sale at The Aquatic Design Centre in London earlier this year. They're quite unusual and not often imported, but not exceptionally rare.
Price: Typical prices are around 3-5.
This article was first published in the Christmas 2004 issue of Practical Fishkeeping magazine.