Not furry, but we like them anyway.
Medaka
Oryzias latipes
Also called Japanese rice fish, Japanese killifish
From Japan, where it lives in rice paddies, ponds, marshes and slow streams of Honshu, Shikoku and Kyushu. Older sources include wider East Asian populations now often treated as separate species.12
At a glance the quick version
Looks how to spot one
Small, slender scaled fish
A small, slim fish with a flat back, upturned mouth and large eyes. Males have longer rays in the dorsal and anal fins than females, which helps tell the sexes apart.23
Personality what they are like
A peaceful, gentle fish that lives in schools and can even recognise individual tankmates by their faces.23
Daily activity how busy a day looks
An active surface-swimming fish that does best in a group with open water near the top.13
Grooming and care the hands-on bits
Easy to maintain. Prefers cooler water and usually needs no heater in a temperate room; keep similar-sized, peaceful companions.13
Home where they are happiest
Aquarium of at least about 45 x 30 cm (around 40 litres) or a pond or patio tub. Water about 16 to 24 °C (survives a far wider range), pH roughly 6.5 to 8.5, hardness 5 to 25 dGH.123
Food basics what goes in the bowl
Omnivore and micropredator. In nature it eats mosquito larvae and plankton; in captivity small live or frozen foods (daphnia, brine shrimp, chopped bloodworm) plus good flakes or granules.123
Company who they like around
The story where it all began
Medaka have been kept as pets in Japan since the 17th century, making them one of the oldest pet fish there. In the 20th century they also became an important laboratory animal thanks to their hardiness and short generation time.23
Fun facts for the dinner table
- 1
Medaka were the first vertebrates to mate in orbit, with healthy fry hatching aboard the Space Shuttle Columbia in 1994.2
- 2
Medaka can survive water temperatures from near freezing up to about 42 °C.2
- 3
Females carry their egg cluster for a while before attaching it to plants.1
- 4
Medaka was the first non-mammal vertebrate in which a sex-determining gene (DMY) was identified.2
Recognised by the official bits
- IUCN Red List
- Assessed as Least Concern (1 March 2018).1
- Fishkeeping
- Hundreds of commercial strains (around 456 cited) are bred for the hobby.2
- Science
- A long-established laboratory model organism.2
The care rhythm Furry Diary remembers it for you
A typical home-care rhythm for a Medaka. It is our own starting plan, not a vet's advice, and you can change every line in the app.
- FeedingSmall amounts once or twice a dayevery day
- Temperature checkevery day
- Water changeAbout 25% of the waterevery week
- Water testevery week
- Glass cleanevery week
- Filter rinseRinse in old tank water, never tap waterevery month
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Where this comes from
Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at [email protected] and we will fix it.
- FishBase: Oryzias latipes fishbase.seused for range, size, temperature, pH, hardness, habitat, diet, IUCN, egg carrying
- Wikipedia: Japanese rice fish en.wikipedia.orgused for range, size, lifespan, colours, history, research, space flight, schooling
- Seriously Fish: Oryzias latipes seriouslyfish.comused for tank size, water parameters, diet, group size, sexing, colour forms
Checked 2026-09-30. Text is written in our own words from these sources.