Koi or more specifically nishikigoi are ornamental domesticated varieties of the common carp that are kept for decorative purposes in outdoor ponds and water gardens. They are also called Japanese carp.
Koi were developed from common carp in ancient China in Jin Dynasty and was later transferred to Korea and Japan, and are still popular there because they are a symbol of love and friendship. A variety of colors and color patterns have since been developed; common colors include white, black, red, 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.