Sweet corn is not considered toxic to koi, but it is harder to digest than a quality koi pellet and should stay an occasional treat. Offer only plain, soft, cooked kernels with the tough outer skin removed or mashed when possible.
Neither sweet corn nor field corn is ideal for koi. However, sweet corn is generally considered slightly better due to its higher sugar content, which may make it more palatable.

Guide to homeade koi food recipe ideas and how to make your own koi pellets. Info about the best ingredients, and recipes for both pellets and paste.

As we can see from the illustration, Making Koi Food With Sweet Corn has many fascinating aspects to explore.
Avoid foods high in moisture and carbohydrate, such as peas, potatoes and sweet corn. Twenty years ago these were koi staples, but only because nothing better was available.

Learn what koi fish eat, what foods to avoid, and how to feed them properly. Covers pellets, treats, seasonal feeding schedules, and hand-feeding tips.