Having koi myself I asked this years ago and the majority of those who answered said that koi should not be fed high protien food when the water temp is below 55 degrees as it can cause the food to rot in their stomach due to lack of digestion. During the colder times koi will eat moss and other things in the pond and do just fine. My koi are spoiled and live in a 3000 gallon pond inside a heated greenhouse so they get to eat year round.

Bob