In the fall, I gradually back off on the amount I feed the fish as the
temp drops. Then when the pond water hits 50 degrees, I completely
shut off the groceries and don't give them anymore until the water temp
is consistently back to 50 or higher in the spring. In the cold
months, the fish are inactive and need very little food, and they can
get what little they do need from what's already there. So the only
reason we are tempted to feed them in the winter is that it entertains
us - not that the fish really need the food. When they do come up to
the surface on a warm winter day, I just take that opportunity to play
with them but don't give them any snacks.

Gary