Kujaku

Cyprinus rubrofuscus

Metallic luster combines with reticulation and red markings.

Adult length: Up to 28 cm (standard length, without the tail fin)

Natural habitat: The species inhabits freshwater and can tolerate slightly brackish conditions; koi are domesticated ornamental forms.

Plan filtration and adult space for a large pond fish; unprotected planting can be damaged.

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Appearance and identification

Compare the continuous metallic sheen on the head, body and fins with nonmetallic Goshiki.

Same-species behaviour

Monitor females during spawning chases; a verified group size and sex ratio are not adopted.

Space requirements

Requires a large pond, effective filtration and ongoing water-quality management. Broad pond-volume guidance lacks a complete adult population context and cannot set stocking capacity.

Diet and feeding

Use appropriate koi feed and adjust to temperature and feeding response; omnivory does not mean reliance on leftovers.

Compatibility limits

Assess size, feeding and spawning behaviour separately; shared pond context or temperature overlap does not prove compatibility.

Aquarium environment

Protect roots and planting areas; colour, scale and fin forms do not remove adult space or water-quality requirements.

Sources

jnpa.info ↗

nas.er.usgs.gov ↗ 2026-10-22

www.fishbase.se ↗ 2026-10-25

nationalzoo.si.edu ↗ 2026-10-22

ornamentalfish.org ↗ 2026-10-22

nwkg.org ↗ 2026-10-22

researcharchive.calacademy.org ↗ 2026-10-22