Koi

Koi , or more specifically nishikigoi (錦鯉, Japanese: [ɲiɕi̥kiꜜɡoi], literally "brocaded carp"), are colored varieties of carp (Cyprinus sp.) that are kept for decorative purposes in outdoor koi ponds or water gardens. Koi is an informal name for the colored variants of carp kept for ornamental purposes. There are many varieties of ornamental koi, originating from breeding that began in Niigata, Japan in the early 19th century.

Source: Wikipedia