Japanese Butterfly Koi

Japanese Butterfly Koi (Cyprinus rubrofuscus) is a butterfly koi with elongated, flowing, sail-like fins — the dorsal, pectoral, and caudal fins trail gracefully as the fish moves, creating a fish that is simultaneously more dramatic and more elegant than standard-fin koi. The fins continue growing throughout the fish's life. This is a Japanese Import koi — one of the most prestigious ornamental fish in the world, with a breeding tradition spanning over 200 years in Japan. Koi are bred in an extraordinary variety of named pattern classifications — Kohaku (red on white), Sanke (red and black on white), Showa (black with red and white), Utsuri, Bekko, Asagi, and many more — each with its own aesthetic standards and breeder community.

Feeding & Care Tip: Sera Koi Royal Mini Nature Food is ideal for smaller and younger koi. As fish grow, transition to Sera Koi Royal Medium Nature Food. Feed 2–3 times daily — only what the fish consume within 5 minutes. Koi are opportunistic omnivores that will also enjoy treats of watermelon, orange slices, and leafy greens placed at the pond surface. Stop feeding when water temperatures drop below 50°F (10°C) — koi metabolism slows dramatically in cold water and uneaten food will foul the pond.

Koi require a substantial pond — at minimum 1,000 gallons for a small group, with an additional 250–500 gallons per adult fish as they grow. A 24-inch depth minimum provides protection from temperature extremes and predators. Powerful biological and mechanical filtration is essential — koi produce enormous amounts of waste relative to their size. A UV sterilizer helps maintain water clarity. Regular partial water changes of 10–25% weekly maintain water quality. Predator protection — netting, motion sensors, or decoys — is strongly recommended as herons, raccoons, and other wildlife will target koi.

Butterfly koi (also called Dragon carp or longfin koi) were developed through crossing standard koi with Indonesian longfin wild carp strains. The result is a fish with the color patterns of koi and the dramatically flowing fins of the longfin carp parent. Japanese Butterfly koi are bred to the same exacting standards as standard Japanese imports.

Koi are among the longest-lived of all ornamental fish — well-kept specimens regularly reach 25–35 years, and the oldest documented koi lived over 200 years. They develop genuine recognition of their keepers over time and can be trained to hand-feed. The investment in a properly sized, well-filtered pond is rewarded with fish that become genuine long-term companions of extraordinary beauty.

Care & Ideal Parameters