This painting i did refers to love and affection in bonding and togetherness. Koi fish are very closely related to goldfish and, in fact, the style of breeding and ornamentation has become very similar, probably through the efforts of Japanese breeders to emulate goldfish. Koi and tattoos of koi are traditionally considered lucky.
The word "koi" comes from Japanese. The original Japanese word koi simply means "carp," including both the dull grey fish and the brightly colored varieties. A homonym of koi means 'love, affection' and koi are therefore symbols of love and friendship in Japan.