Koi feed at the surface of a pond. Koi, or nishikigoi, literally 'brocaded carp', are ornamental domesticated varieties of the common carp, Cyprinus carpio. They are very closely related to goldfish. Koi varieties are distinguished by coloration, patterning, and scalation. Koi have many different colors. Some of the major colors are white, black, red, yellow, blue, and cream.