All fish / Poeciliidae

Least Killifish

Heterandria formosa

Also known as least killifish, dwarf livebearer, mosquitofish dwarf, midget livebearer, formosa, least livebearer, dwarf topminnow, ヘテランドリア・フォルモサ, 小型食蚊鱼, 侏儒花鳉

One of the smallest fish in the world, this livebearer is olive brown with a dark stripe along the side and a dark spot on the dorsal fin. Males reach barely 2 cm and females about 3 cm. It suits planted nano tanks and is valued for its hardiness and unusual breeding habits.

Care at a glance

Care level

Easy

Temperament

Peaceful

Adult size

2.5 cm

Temperature

20 to 28 °C

pH

7 to 8

Smallest tank

20 litres

Keep as

Group of 6 or more, more females than males

Diet

Omnivore: fine flake, micro pellets, baby brine shrimp, daphnia, microworms

Swims

Middle of the tank

Lifespan

2 to 3 years

Water

Freshwater

Wild range

Southeastern USA (North Carolina to Florida and Louisiana)

Breeding

Females give birth to one or two fry every few days over a long period thanks to superfetation, rather than large broods at once. Breeding is easy in a densely planted species tank, and adults rarely eat the young.

Good to know

Too small to share a tank with most other fish, as even modest tankmates may eat or bully it. It tolerates cooler water and does not need a heater in a warm room.