What tank size does a Medaka Ricefish need?

A Medaka Ricefish needs an aquarium of at least 40 litres (10.6 US gallons) with a footprint at least 45 cm (17.7 in) long — for this species, swimming length matters as much as raw volume.

What water parameters does a Medaka Ricefish need?

Medaka Ricefish does best at 8–28 °C (46.4–82.4 °F), pH 6.5–8.5 and a general hardness of 5–25 °dGH.

What group size does a Medaka Ricefish need?

Medaka Ricefish is a social species — keep a group of at least 8 so natural behaviour emerges and stress stays low.

Is the Medaka Ricefish suitable for beginners?

Yes — Medaka Ricefish is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.

Species library

Medaka Ricefish

Oryzias latipes

Adrianichthyidae

FishDifficulty: ●●○○○Data: well-established

📷 Seotaro · CC BY-SA 3.0 · resized · Wikimedia Commons

Medaka Ricefish — Oryzias latipes — 📷 Seotaro · CC BY-SA 3.0 · resized · Wikimedia Commons

About

The medaka, or Japanese rice fish, is a 3-4 cm surface-dwelling fish from the rice paddies, ditches and slow streams of Japan, Korea, China and Vietnam. Kept ornamentally in Japan for centuries and used worldwide as a laboratory model organism, it is calm, tolerant and undemanding, and it needs no heater in a normally heated home — one of the very few genuinely good choices for an unheated room-temperature tank. Females carry a visible cluster of eggs trailing from the vent before attaching them to plants, so spawning happens in plain view and fry appear without any intervention.

Care

Keep eight or more in 40 L or larger with a base at least 45 x 30 cm, unheated at 16-22°C with gentle flow. A tight lid is essential — this is a surface fish and it jumps. Floating plants give both cover and spawning sites.

Diet

Micropredator taking insects, worms, crustaceans and zooplankton in nature; feed quality flake and micro-granules plus daphnia, artemia and chopped bloodworm. It feeds at the surface, so sinking food goes to waste.

Tankmate compatibility

Gets along with (15)

Butterfly Hillstream Loach Denison Barb Doctor Fish Glowlight Danio Gold Barb Japanese Trapdoor Snail Least Killifish Leopard Danio Odessa Barb Pearl Danio Rosy Barb Rosy Red Minnow Rubber Lip Pleco White Cloud Mountain Minnow Zebra Danio

Possible with care (208)

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Avoid (48)

Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.

Telling males from females

What works for this species, most reliable first.

Colour and patternA hint only · from about 6 months, and only on a settled fish
In rainbowfish, killifish and several barbs the male carries the colour — deeper and more saturated, intensifying further when he displays.

All the methods, with diagrams

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Frequently asked questions

What tank size does a Medaka Ricefish need?: A Medaka Ricefish needs an aquarium of at least 40 litres (10.6 US gallons) with a footprint at least 45 cm (17.7 in) long — for this species, swimming length matters as much as raw volume.
What water parameters does a Medaka Ricefish need?: Medaka Ricefish does best at 8–28 °C (46.4–82.4 °F), pH 6.5–8.5 and a general hardness of 5–25 °dGH.
What group size does a Medaka Ricefish need?: Medaka Ricefish is a social species — keep a group of at least 8 so natural behaviour emerges and stress stays low.
Is the Medaka Ricefish suitable for beginners?: Yes — Medaka Ricefish is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.

Sources

Water & tank

Temperature8–28°C

Optimal temp.16–22°C

pH6.5–8.5

Hardness (GH)5–25°d

Carbonate (KH)3–15°d

Adult size4 cm

Min. volume≥ 40 L

Min. tank length≥ 45 cm

Group size≥ 8

Swimming zoneTop

TemperamentPeaceful

Water typeBrackish-tolerant

FlowLow

Lifespan~3 yrs

Try in the calculator