Koi is the domesticated coloured form of the wild common carp (Cyprinus carpio), native fish of the slow-moving waters of Eurasia and the Middle East. Although it is the national fish of Japan, it is thought that the fish was originally introduced to Japan from the land around Iran.
"KOI" it name are from the translated of Japanese words into English, it is possible for words to be spelled in two ways. In may cases "KOI" is called "GOI", either is correct the Japanese refer to carp as "goi" or "koi" and nishike means coloured, so another popular name is nishiki-goi (Coloured carp).
Koi may reach a length of 120cm and weight of 15 kilogram or more and its live spans of 30 years or more. Colour of Koi may linked to size and age of the fish, the largest or the mature fish are invariably of the most well established colour.