Butterfly Splitfin

The sole member of its genus, Ameca splendens belongs to the Goodeidae, a family of Mexican livebearers still little known in the hobby. Males stay smaller and carry the broad, bright yellow band along the edge of the tail that earns the fish its name; females grow bulkier, to around ten centimetres, and keep a plainer olive-grey. The species is confined to the Río Ameca basin in Jalisco, western Mexico, its type locality the Río Teuchitlán. These are clear, well-oxygenated spring waters with a noticeable current. Long reported extinct in the wild, it clings on at a handful of sites and is listed as critically endangered by the IUCN, which makes aquarium stocks a genuine reservoir. Hardy, but far from easy-going: males can be quite aggressive and the species makes a poor community fish. Keep a group of at least six, two or three females per male, in 200 litres with an open floor (90 cm front minimum) and roots or planting to break sightlines. Feed mostly vegetable matter. After 55 to 60 days, females drop 5 to 30 unusually large fry.