Medaka
Oryzias latipes
The Japanese rice fish: hardy, peaceful and ideal for an unheated tank or a summer pond, with hundreds of ornamental strains.
Key facts
- Body length
- 1.4 in without fins
- Minimum tank
- 13 gallons
- Group
- 6+
- Temperament
- Peaceful
- Care level
- 1 / 5
- Lifespan
- Not well documented
- Diet
- Micro pellets, flakes, baby brine shrimp, daphnia
- Origin
- Japan, Korea, Taiwan and eastern China
- Hardier than87%
- Bigger than16%
- Calmer than68%
Water: their range vs yours
Medaka tank mates
- Neon tetraGets along in shared water.Good mates
- Harlequin rasboraGets along in shared water.Good mates
- Fancy guppyGets along in shared water.Good mates
- Panda corydorasGets along in shared water.Good mates
- OtocinclusGets along in shared water.Good mates
- Cherry shrimpGets along in shared water.Good mates
- BettaGets along in shared water.Good mates
- Tiger barbGets along in shared water.Good mates
- Amano shrimpGets along in shared water.Good mates
- Black neon tetraGets along in shared water.Good mates
- Black widow tetraGets along in shared water.Good mates
- Blood parrot cichlidGets along in shared water.Good mates
- Chinese algae eaterChinese algae eater attacks fish with a similar shape or colour: Japanese rice fish (medaka).Risky
- Clown loachClown loach attacks fish with a similar shape or colour: Japanese rice fish (medaka).Risky
- DemasoniDemasoni attacks fish with a similar shape or colour: Japanese rice fish (medaka).Risky
- Golden mbunaGolden mbuna attacks fish with a similar shape or colour: Japanese rice fish (medaka).Risky
- Peacock cichlidMalawi butterfly peacock attacks fish with a similar shape or colour: Japanese rice fish (medaka).Risky
- Rainbow sharkRainbow shark attacks fish with a similar shape or colour: Japanese rice fish (medaka).Risky
- AngelfishAngelfish can eat Japanese rice fish (medaka): prey body depth 0.8 cm ≤ mouth 2.3 cm.Avoid
- Blue dolphin cichlidBlue dolphin cichlid can eat Japanese rice fish (medaka): prey body depth 0.8 cm ≤ mouth 6.3 cm.Avoid
- Convict cichlidConvict cichlid can eat Japanese rice fish (medaka): prey body depth 0.8 cm ≤ mouth 3.8 cm.Avoid
- Firemouth cichlidFiremouth cichlid can eat Japanese rice fish (medaka): prey body depth 0.8 cm ≤ mouth 3.0 cm.Avoid
- GoldfishGoldfish can eat Japanese rice fish (medaka): prey body depth 0.8 cm ≤ mouth 3.0 cm.Avoid
- Iridescent sharkIridescent shark can eat Japanese rice fish (medaka): prey body depth 0.8 cm ≤ mouth 32.5 cm.Avoid
How we check
The numbers the tank model uses for medaka: water as ideal and tolerated ranges, bioload from adult mass, space, flow and how they act on other species.
- Standard length
- 3.6 cm (SL)
- Adult mass
- 0.47 g
- Bioload at 25 °C
- 0.62 BU
- Min. water
- 41 L net
- Min. footprint
- 45 × 30 cm per group
- Group
- 6+ (best 8)
- Swims in
- top
- Flow
- low
- Body / fins
- fusiform, normal fins
- Diet type
- micropredator
- Fin nipper
- none
- Sensitive to
- —
Sources: Seriously Fish: Oryzias latipes · FishBase: Oryzias latipes
Care notes
Medaka come from rice paddies, canals and streams across Japan, Korea, Taiwan and eastern China and grow to about 1.5 inches. They stay near the surface and are confident in groups of eight or more.
A 10-gallon tank at 64–72 °F needs no heater, and constant warmth probably shortens their life. Do not mix them with other Oryzias species, which they hybridise with.
Questions
What size tank does a medaka need?
At least 13 gallons (41 litres of water after decor). Adults reach about 1.4 inches without fins.
How many medaka should be kept together?
Keep at least 6, ideally 8 or more: fewer feel exposed and hide or turn nippy.
What water do medaka need?
64–72 °F, pH 6.5–8.5 and 5–25 dGH. Medaka come from Japan, Korea, Taiwan and eastern China.
How long do medaka live?
Not well documented with good care.
What fish can live with medaka?
Good tank mates include Neon tetra, Harlequin rasbora, Fancy guppy, Panda corydoras and Otocinclus. Each is checked both ways for size, fin nipping, temperament, territory and shared water.