Known as Nishikigoi by the Japanese, koi fish have mainly been kept for their aesthetic appeal and bright colors. Frequenting in many ponds and outdoor water gardens, this species of fish feed on pond plants and can also be hand fed. They can grow to over two feet long with an average lifespan of an astonishing 50 years. There are known to be close to one hundred different varieties of koi fish available today, so which one is right for you and your home? We have compiled a list of seven varieties of koi fish which may be of interest in your passion of koi fish.