When selecting the proper food for your Koi the first ingredient should be listed as fish, followed by fish meal and other fish products. Foods where corn is listed as the first ingredient, while more economical, tend to make for overweight and unhealthy Koi.
The nutritional needs of Koi will vary throughout the year depending on temperature and season. In warmer times, above 61 degrees Fahrenheit or 46 Celsius, the Koi will be more active and require more feedings, at least twice a day or more.
During these warmer times, when they will require more feedings, it is best to provide these as small meals throughout the day. Koi do not have stomachs and won’t ever feel full, as a result, they will eat whatever is provided. Overfeeding will cause an over accumulation of waste which will result in the polluting of the water.
As it gets cooler, between 56-60 F or 43-45 C and the fish become less active, it is only necessary to feed once a day. The schedule is reduced to no more than three times weekly when the temperature is between 46-50 F and 38-40 C. The fish require no feeding when the temperature dips below 46 degrees F, 38 C.
Koi are adventurous diners and will enjoy such treats as shrimp, cut into pieces according to the size of the fish, watermelon, oranges and even grapefruits. Citrus fruits are a natural source of vitamin C and are wonderful for ailing fish as well.
They will enjoy most greens and vegetables, but stay away from spinach, cabbage and zucchini and they don‘t seem to like bananas.
For the most part Koi will eat a wide variety of foods and it is a trial by testing to see on which diet your particular Koi will thrive.