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Oryzias latipes var.
Improved Youkihi with deeper, more intense crimson. The name 'Koutei' reflects its regal red. Color deepens outdoors.
Koutei (Red Emperor) medaka is a further improved variant of Youkihi featuring an even deeper and more intense crimson-vermilion coloration. The name evokes the overwhelming red presence of an emperor. Multi-generation selective breeding produces lines with particularly excellent coloration approaching true 'deep crimson.' Outdoor sunlight deepens color further; astaxanthin- and carotenoid-rich color-enhancing food maintains and strengthens coloration. Dark containers and outdoor lotus pots best showcase the deep crimson. Breeding is as easy as Youkihi, with color-quality improvement through selective pairing.
The Koutei Medaka lives 2-3 years.
The Koutei Medaka grows to 3-4cm.
The ideal temperature for the Koutei Medaka is 18〜24℃.
Hardy in 5–30°C, neutral to slightly alkaline water.
Origin
Japan (selectively bred variety)
Lifespan
2-3 years
Size
3-4cm
Temperature
5〜30℃
Sources: FishBase: Oryzias latipes / Seriously Fish: Oryzias latipes
Selectively bred killifish are trait combinations of body form × body color × pattern × luminescence (internal/external) × scale types (transparent scales) × sparkle × fin morphology and so forth. Published entries include only confirmed traits constituting the given variety, with genetic inheritance patterns provided only for confirmed traits (uncertain cases omitted). Genetic patterns are provided as reference for breeding.
Sources: JMA Japan Medaka Association — Improved Medaka Variety Classification Manual (JA) / Improved Medaka Web Encyclopedia (medakazukan, JA)
A curated selection of notable morphs. Inheritance modes are a breeding-planning guide; actual appearance varies with combos.
Edited & verified by: BreederDirect editorial team
The taxonomic, regulatory, and husbandry data on this page are compiled and verified against the authoritative primary sources below.
Accepted name: Oryzias latipes var. (Temminck & Schlegel, 1846)
Synonyms: Aplocheilus latipes (Temminck & Schlegel, 1846), Poecilia latipes Temminck & Schlegel, 1846, Oryzias latipes latipes (Temminck & Schlegel, 1846)
Authority databases: FishBase · GBIF · Japan Medaka Association — Variety Classification Manual (JA)
Nomenclature follows global taxonomic authority databases.
Find listings for this species
Medaka pellets, daphnia
A black container brings out the deep crimson best. An outdoor water-lily bowl is also ideal.
Keeping it outdoors in sunlight deepens the body color further, so place it in a sunny spot.
Adapts to 5-30°C (ideally 18-24°C) and neutral to slightly alkaline water and is easy to keep. Can overwinter outdoors.
Combining red color-enhancing food rich in astaxanthin and carotenoids maintains and strengthens the coloration.
Breeding is easy, much as with Yang Guifei medaka. Pairing the most deeply colored fish maintains quality.
Intermediate. This is an intermediate-level species. Some prior experience and knowledge of environmental management are recommended.
The ideal temperature for Koutei Medaka is 18〜24℃. Avoid sudden temperature changes and maintain a stable environment.
The average lifespan of Koutei Medaka is 2-3 years. With proper care and nutrition, they can live a long and healthy life.
Koutei Medaka typically reaches 3-4cm as an adult. Size may vary depending on care conditions and individual genetics.
Koutei Medaka feeds on: Medaka pellets, daphnia. Aim for a balanced diet with appropriate feeding frequency.
The price of Koutei Medaka varies significantly depending on morph, size, and lineage. Check our market price page for the latest pricing information.
Last updated: August 31, 2026