Koi (鯉, English: /ˈkɔɪ/, Japanese: [koꜜi]) or more specifically nishikigoi (錦鯉, [ɲiɕi̥kiꜜɡoi], 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.


Several koi swim around in a pond in Japan
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, and cream. The most popular category of koi is the Gosanke, which is made up of the Kohaku, Taisho Sanshoku, and Showa Sanshoku varieties.

History
Carp are a large group of fish originally found in Central Europe and Asia. Various carp species were originally domesticated in East Asia, where they were used as food fish. Carp are coldwater fish, and their ability to survive and adapt to many climates and water conditions allowed the domesticated species to be propagated to many new locations, including...