Adequate koi food contains 32 to 36 percent protein from fish by-products as its first ingredient. Its second ingredient is plant matter, from sources like wheat germ, that gives an energy boost. Koi food should also contain 3 to 10 percent crude fat, ascorbic acid, immune boosters and color enhancers.
Because koi are omnivores, they need a varied diet that is high in protein to stay healthy. KoiVet.com recommends using a food that contains a high percentage of protein from fish meals like squid meal, whitefish meal, anchovy meal, shrimp meal or herring meal. Because koi fish have no stomachs, they can eat only a little at a time, so high-quality, balanced feed gives them the best nutrition in several small feedings a day.