A hardy, small, and colorful fish native to East Asia. Extremely popular in the outdoor pond hobby and nano aquariums. They are 'amphidromous' (tolerant of salinity changes) and can survive a wide range of temperatures, making them excellent tub/pond fish. They are surface dwellers that look best when viewed from above (top-down).
At a Glance
Tank Requirements
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Water Parameters
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Temperament & Compatibility
Available Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard (Short Fin)
The typical form found in both ponds and aquariums. Includes famous color strains like Youkihi (Orange), Miyuki (Blue/Silver), and various sparkle (Lame) morphs. Extremely active and hardy.
Differs in 1 trait from base species
Also known as: Wild Type, Orange, Youkihi, Platinum, Miyuki, Galaxy, Lame, Tri-color
Long Finned
Selectively bred variants with extended dorsal and anal fins. These fish are not as agile as short-finned varieties and require strictly low flow to thrive. They should not be kept with fin-nippers.
Differs in 3 traits from base species
Also known as: Swallow, Wind, Real Long Fin, RLF
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🟢Ideal Tank MatesJapanese Ricefish (Medaka) Care Guide Summary
The Japanese Ricefish (Medaka), scientifically known as Oryzias latipes, belongs to the Killifish family group. Adults reach a maximum size of approximately 4 cm and have a fusiform body shape with a moderate growth rate. Classified as peaceful, this species primarily occupies the surface zone of the aquarium and produces a low level of biological waste.
To thrive, the Japanese Ricefish (Medaka) requires a brackish tolerant aquarium with a minimum volume of 19 litres and a tank length of at least 30 cm. Water temperature should be maintained between 10°C and 28°C, with a pH range of 6.5–8.5 and a general hardness of 5–25 dGH. A low water flow is preferred. An aquarium test kit can help you monitor these values.
The Japanese Ricefish (Medaka) is a rewarding species to keep, provided its core environmental needs are met. This species is available in 2 varieties: Standard (Short Fin) and Long Finned. Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
Japanese Ricefish (Medaka) Habitat Setup
When setting up an aquarium for the Japanese Ricefish (Medaka), a low water flow best suits their natural preferences. Because this species occupies the surface zone, the aquarium layout should prioritise adequate surface area with floating cover to make them feel secure near the waterline. Useful additions include dense planting to provide cover, break sightlines, and reduce stress and floating plants to diffuse overhead light and create shaded areas. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper.
Japanese Ricefish (Medaka) Compatibility Notes
Classified as peaceful, the Japanese Ricefish (Medaka) is a schooling species that feels most secure in a sizeable group, where natural shoaling behaviour reduces stress and brings out their best colours. When choosing tankmates, their energetic swimming style may stress more sedentary or timid species. Selecting tankmates that favour different water layers from the surface zone can help reduce competition and territorial overlap.
Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Japanese Ricefish (Medaka).
5 Gallon
10 Gallon Standard
15 Gallon Standard
20 Gallon High
20 Gallon Long
29 Gallon Standard
Show 27 more tank sizes
Frequently Asked Questions About Japanese Ricefish (Medaka)
How big does Japanese Ricefish (Medaka) get?
Japanese Ricefish (Medaka) (Oryzias latipes) typically reaches a maximum adult size of approximately 4 cm. They have a fusiform body shape and a moderate growth rate.
What tank size does Japanese Ricefish (Medaka) need?
A minimum aquarium volume of 19 litres and a tank length of at least 30 cm are recommended for Japanese Ricefish (Medaka). This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Japanese Ricefish (Medaka) need?
Japanese Ricefish (Medaka) thrives in brackish tolerant conditions with a temperature range of 10–28°C, a pH between 6.5 and 8.5, and a general hardness of 5–25 dGH. A low water flow is preferred.
Is Japanese Ricefish (Medaka) peaceful or aggressive?
Japanese Ricefish (Medaka) is classified as peaceful with an aggression score of 2 out of 10. They are generally well-suited to peaceful community tanks.
How many Japanese Ricefish (Medaka) should be kept together?
Japanese Ricefish (Medaka) is a schooling species and should be kept in groups of at least 6. Larger groups help distribute aggression and encourage natural schooling behaviour.
Does Japanese Ricefish (Medaka) have any special tank requirements?
Yes. Japanese Ricefish (Medaka) benefits from plants - densely covered and plants - floating in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Does Japanese Ricefish (Medaka) need a lid on the tank?
Yes. Japanese Ricefish (Medaka) is a known jumper, and a tight-fitting lid or cover is essential to prevent escape. Even a small gap can be enough for a determined fish to leap out.
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