Medaka Ricefish (Oryzias latipes) Care Guide
A tiny, elegant Japanese fish that has surged in popularity worldwide. Extremely hardy and cold-tolerant, it thrives in outdoor tubs and indoor nano tanks alike.
Compiled by Aquairi from published sources · Published · Updated
Overview
Oryzias latipes is a species in the family Adrianichthyidae. A tiny, elegant Japanese fish that has surged in popularity worldwide. Extremely hardy and cold-tolerant, it thrives in outdoor tubs and indoor nano tanks alike. Available in many selectively bred color varieties including orange, platinum, and blue. One of the few fish comfortable in both cool and warm water.
Taxonomy
- Family: Adrianichthyidae
- Genus: Oryzias
- Scientific name: Oryzias latipes
- Other names: Japanese Ricefish, Japanese Killifish, Oryzias
- Origin: East Asia, Japan, Korea, China
Habitat
Native to East Asia including Japan, Korea, China and Vietnam. Inhabits still and slow-moving fresh and brackish waters such as rice paddies, ditches and ponds. Highly tolerant of temperature and salinity fluctuations; a long-established model organism in biology.
Tank requirements
- Minimum tank volume: 20 L
- Temperature: 4-30 °C
- pH: 6.5-8
- GH: 5-20 °dGH
- Water flow: low
- Adult size: 3-4 cm
- Lifespan: 2-4 years
- Recommended group size: ≥ 6
- Difficulty: beginner
Diet
Classified as omnivore. Recommended feeding frequency: 2x daily. In captivity, offer a varied diet appropriate to the species — quality prepared foods supplemented with frozen or live items of suitable size.
Compatibility
- Temperament: peaceful
- Swimming level: top
- Compatible tank mates: Cherry Shrimp, Nerite Snail, White Cloud Minnow, Corydoras
- Avoid with: Large Fish, Aggressive Fish, Betta
Breeding
- Breeding strategy: egg-depositor
- Breeding difficulty: beginner
Medaka Ricefish (Oryzias latipes) Breeding Guide
Overview
Oryzias latipes is described as quite easy to breed and fairly prolific. Females in good condition can produce batches of eggs every few days or even on a daily basis. Spawning typically follows the warmer, longer days of spring and summer, and the species responds to photoperiod and temperature.
Sexing
Males have elongated, filamentous rays in the convex dorsal and anal fins, bony contact organs on the medial pectoral-fin rays and posterior anal-fin rays, and a slightly slimmer body than females. The male's genital papilla forms a short tube. Females have non-convex dorsal and anal fins and a bilobed genital papilla, and ripe females are rounder-bodied.
Conditioning
Condition the group well, as females in good condition spawn most frequently. The species reproduces within its preferred temperature band of roughly 15-28 °C (59-82 °F); breeding activity increases toward the warmer end of that range and under longer day length.
Breeding Setup
Provide fine-leaved plants such as Cabomba, Ceratophyllum or Taxiphylum (java moss), or synthetic spawning mops, to receive the eggs. A densely planted tank also gives free-swimming fry cover from adults.
Spawning Behavior & Trigger
Spawning normally occurs in the early morning. Males darken in colour and defend small, temporary territories against one another while enticing females. The adhesive eggs are expelled as a single mass and fertilised simultaneously; the female then carries the cluster hanging from her genital pore for a period before depositing the eggs singly or in small clumps among vegetation.
Egg & Fry Care
Incubation is temperature dependent, typically 1-3 weeks (eggs commonly hatch in about 4-10 days in warmer water). Adults tend to ignore the eggs but will eat free-swimming fry, so a densely planted tank or removal of eggs to a separate container improves survival. Once free-swimming, fry accept microworm and Artemia (brine shrimp) nauplii.
Common Challenges
Predation of free-swimming fry by adults is the main loss point; dense planting or moving eggs addresses it. Because females spawn so readily, the limiting factor is usually fry-rearing space and a steady supply of suitably small first foods rather than getting eggs in the first place.