Japanese Standard Fin Koi

Japanese Standard Fin Koi (Cyprinus rubrofuscus) is a standard fin koi with traditional koi body and fin shape — the classic silhouette that has defined koi keeping for centuries. The standard fins are proportional to the body, allowing these fish to swim powerfully and competitively in the pond. 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.

Japanese koi are bred to exacting standards developed over generations of selective breeding. Japanese breeders evaluate koi on the quality and symmetry of color patterns, skin luster, body conformation, and deportment — the way the fish carries itself in the water. A Japanese import represents the pinnacle of the koi breeder's art and typically carries premium lineage.

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