Domestic Butterfly Koi
Domestic Butterfly Koi (Cyprinus rubrofuscus) is a butterfly koi with long, flowing, sail-like fins that trail gracefully as the fish moves. The fins continue growing throughout the fish's life, becoming more dramatic with age. Domestic Butterfly koi are bred in the United States and offer excellent value in the flowing-fin koi category. This is a Domestic (USA-bred) 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.
Domestic Butterfly koi combine the flowing-fin mutation with the hardiness and adaptability of US-bred stock. The butterfly fin mutation means fins will continue growing and developing throughout the fish's life — a 10-year-old Butterfly koi has dramatically more impressive fins than a juvenile. Provide gentle pond flow to keep the long fins in good condition.
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
| Difficulty | Moderate — pond setup required |
| Temperament | Peaceful — social pond fish |
| Typical Adult Size | 24–36 inches (60–90 cm) — some specimens larger |
| Min. Group Size | 3 minimum — 1,000 gallon minimum pond; 250–500 gallons per adult fish |
| Ideal Temp | 35–85°F (2–29°C) — ideal 65–75°F (18–24°C) |
| Ideal pH | 6.5–8.5 |
| Ideal GH | 5–20 dGH |
| Ideal KH | 3–15 dKH |
| Staple Food | Sera Koi Royal Mini Nature Food (juveniles); Sera Koi Royal Medium Nature Food (adults) |
| Treat / Supplement | Watermelon, oranges, leafy greens; Hikari Frozen Baby Brine Shrimp (juveniles) |
| Origin | Japan/USA (captive-bred — all ornamental koi are Cyprinus rubrofuscus) |
| Notes | Domestic (USA-bred) — excellent value in butterfly fin category. Fins grow throughout life — most dramatic in older fish. Gentle flow recommended. |
