Orochi

Orochi key facts

Care level

Beginner-friendly

Lifespan

2-3 years

Size

3-4cm

Diet

Medaka pellets

Container & Tank

With no camouflage response it stays black even in a white container, so a white container makes the jet-black body stand out best.

Water Temperature & Quality

Handles 5-30°C and is relatively easy to keep. Use neutral to slightly alkaline water and change it regularly to keep it clean.

Diet & Feeding

Feed medaka pellets as the staple, in small amounts eaten within a few minutes so leftovers do not foul the water.

Breeding & Egg-laying

Even F1 offspring retain the black well; selecting the blackest fish to breed fixes the trait easily. Widely used as a parent for black varieties.

Health & Cautions

Some individuals have a weaker constitution, so avoid sudden temperature changes and keep water quality stable.

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.

Featured breeders for Orochi

🏠松島弘典 Breeder広島県0 Orochi listings亀田養魚 Breeder栃木県★ 5.0 (1)0 Orochi listings

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.

6. 6Easy to Breed, Egg Care Matters

   Orochi breeds readily like other medaka varieties, typically spawning from spring through summer with adequate light and conditions. Eggs should be moved to a separate container to prevent parents from eating them — spawning mops or moss help collect eggs. Their black coloration is genetically stable and passes reliably to offspring.

7. 7Cost and Choosing Quality Fish

   Orochi prices vary with quality, ranging from a few hundred to several thousand yen per fish, with especially deep-black specimens commanding higher prices. When selecting fish, look for uniform jet-black coloration across the entire body, intact fins, good body shape, and active swimming behavior. Avoid individuals with pale patches or signs of white spot disease.

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.

Q.Can Orochi be kept together with other medaka varieties?

A.Orochi is peaceful and can coexist with other medaka varieties. However, crossbreeding with other varieties will disrupt the fixed black coloration, so single-variety management is recommended for breeding purposes. For display-only tanks, mixed keeping poses few health concerns.

Q.Can you identify Orochi fry at an early stage?

A.Fry do show dark pigmentation from hatching, but the full jet-black coloration stabilizes one to two months after birth. Waiting until the fish mature before making selection decisions is more accurate. Removing individuals with weaker pigmentation from the breeding group helps preserve lineage quality.

Q.Does keeping Orochi require any special equipment?

A.Standard medaka equipment is sufficient for keeping Orochi. For display purposes, using a black tub or container enhances the fish's appearance significantly. Orochi is not fond of strong currents, so if using a filter, set it to a low flow rate.

Q.What causes Orochi's black color to appear faded?

A.Deteriorating water quality, stress, or nutritional deficiency can affect how the coloration appears. Moving the fish to a lighter-colored container may also make the black seem less intense due to reduced contrast. Start by performing a water change and checking the container color, then monitor the fish's condition.

Useful tools for Orochi care

Learn more about Orochi in the encyclopedia

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