Blue lyretail

Gardner's killifish is a small West African toothcarp from the Cross River and Benue drainages of Nigeria and Cameroon. In the wild it lives in shallow, soft, acidic water — brooks, swamps and forest pools that are sometimes only a few centimetres deep and, in places, dry down seasonally. It is sold in the trade as the blue lyretail, and most aquarium stock descends from hardy line-bred strains.

A mature male is the reason people keep the fish: a sky-blue body flecked with red, fins edged in yellow, and a tail drawn out into the lyre shape that gives it its common name. Females are plain tan by comparison. Males reach around 5.5 cm and stay a little larger than females.

This is not a community fish. Males spar with one another and harass females, so the usual approach is one male to two or three females in a well-planted tank of about 60 litres with plenty of broken sightlines. Keep the water soft and tannin-stained — a sponge filter, dark substrate and some leaf litter suit it — at 20–26 °C and a pH of 6.0–7.5. A tight lid is not optional; these fish jump.

Feeding is easy as long as the food moves. It is a micropredator that takes small live and frozen fare such as daphnia, brine shrimp and bloodworm, and only sometimes accepts dry food. That same appetite makes it unsafe with dwarf shrimp, which it will hunt. It is a non-annual spawner: a conditioned pair lays a few eggs a day among fine plants or a spawning mop, and the eggs hatch in roughly two to three weeks.