Koi (Cyprinus carpio f. domestica)

Koi or more specifically nishikigoi (Japanese: literally "brocaded carp"), are colored varieties of the Amur carp (Cyprinus rubrofuscus) that are kept for decorative purposes in outdoor koi ponds or water gardens.

Koi is an informal name for the colored variants of C. rubrofuscus kept for ornamental purposes. There are many varieties of ornamental koi, originating from breeding that began in Niigata, Japan in the early 19th century. Several varieties are recognized by the Japanese, distinguished by coloration, patterning, and scalation. Some of the major colors are white, black, red, orange, yellow, blue, brown and cream. The most popular category of koi is the Gosanke, which is made up of the Kōhaku, Taishō Sanshoku and Shōwa Sanshoku varieties.

In Aquariums and Zoos: common in european aquariums