Orochi

Orochi key facts

Care level

Beginner-friendly

Lifespan

2-3 years

Size

3-4cm

Diet

Medaka pellets

Container

Maintains black even in white containers

Temperature

5-30°C

Breeding

F1 maintains high black coloring rate

Selection

Select blackest individuals to fix trait

Notes

Some individuals may have weaker constitution

About Orochi

Orochi is a selectively bred medaka variety developed during the ornamental medaka boom in Japan in the early 2000s, its name derived from Yamata no Orochi, the eight-headed serpent of Japanese mythology. Its defining characteristic is a deep, uniform jet-black coloration that does not lighten in response to background brightness — a trait known as the absence of background adaptation response. This intense pigmentation results from the high density and quality of melanophores, and individuals from well-maintained selective lines display a rich, ink-like blackness. Dark-colored containers are standard practice, as light backgrounds diminish the visual impact of the fish. Orochi has a relatively calm temperament and prefers to school, creating a visually cohesive display when kept as a single variety group. At just 3–4 cm when fully grown, they are compact and well-suited to space-efficient setups.

7 things to know before welcoming a Orochi

1. 1Darkness Is Key: Manage Light

   The container and substrate color significantly affect how dark Orochi appears. Using black or dark-colored tanks and substrate enhances the depth of their coloration. Bright or white containers can make them look washed out, so choosing a high-contrast setup is key to showcasing their signature black.

2. 2Fixed Background Adaptation

   Ordinary medaka lighten their color in bright environments through background adaptation, but Orochi has this response genetically fixed, maintaining its black coloration regardless of surroundings. This makes it one of the most stable black varieties available for diverse tank setups.

3. 3Standard Water Quality Care

   Orochi has no special water quality requirements and thrives in the same neutral to slightly alkaline conditions (pH 6.5–8.0) as other medaka. Aim for weekly partial water changes of around one-third to prevent ammonia and nitrite buildup. Poor water quality causes stress and can dull their coloration over time.

4. 4Tank Size and Stocking Density

   Adults reach 3–4 cm and can be kept in multiples in containers as small as 10–20 liters. Avoid overcrowding, as it degrades water quality and increases aggression — a general guideline is one fish per liter. Outdoor pond-style containers are also a suitable option for Orochi.

5. 5Peaceful and Community-Friendly

   Orochi is a peaceful variety well-suited to community tanks with other medaka breeds or small, non-aggressive fish. Avoid housing them with fin-nippers or larger, aggressive species. Keeping them with similarly sized, compatible tankmates minimizes stress and keeps the environment harmonious.

Frequently asked questions about Orochi

Q.Why is it recommended to keep Orochi in dark-colored containers?

A.Although Orochi's color does not change due to the absence of a background adaptation response, white or bright containers cause the black body to blend into the surroundings, reducing visual impact. Dark containers enhance contrast and bring out the full depth of Orochi's jet-black appearance.

Can Orochi be kept together with other medaka varieties?

Useful tools for Orochi care

Learn more about Orochi in the encyclopedia

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