All fish / Adrianichthyidae

Japanese Rice Fish

Oryzias latipes

Also known as medaka, japanese medaka, rice fish, ricefish, golden medaka, japanese killifish, ricefish medaka, youkihi medaka, orange medaka, ปลาข้าวสาร, ปลาเมดากะ, ikan medaka

A small, slim fish with a flat back, upturned mouth and large eyes, found wild in rice paddies and slow streams. Breeders in Japan have produced hundreds of colour and fin strains, from orange and white to metallic-backed and long-finned forms. It is popular because it is hardy, tolerates cool water and suits unheated tanks, bowls and patio ponds.

Care at a glance

Care level

Easy

Temperament

Peaceful

Adult size

3.5 cm

Temperature

18 to 28 °C

pH

6.5 to 8

Smallest tank

40 litres

Keep as

Group of 6 or more

Diet

Omnivore: small flakes, micro pellets, daphnia, brine shrimp and bloodworm

Swims

Top of the tank

Lifespan

2 to 4 years

Water

Freshwater

Wild range

Japan, Korea, eastern China and Taiwan

Breeding

An egg layer that spawns readily, often daily; females carry a cluster of eggs at the vent before brushing them onto plants. Eggs hatch in about 7 to 14 days depending on temperature, and moving them or providing dense plants stops adults eating the fry, so breeding is easy.

Good to know

Adults will eat eggs and fry, so separate them if raising young. It is a widely used laboratory model, and the wild southern population is now often treated as Oryzias latipes while the northern one is Oryzias sakaizumii, so trade fish may be either or hybrids.