Stop at 45 degrees!!!
Fish cannot properly metabolise food beyond that causing bloat and other aliments.
My temp. to food ratio is....
65+ 2-3 times daily w/a high protein, growth and color formula.
55-60 1-2 times daily w/above food.
50-55 Once a day, skipping everyother day.
45-50 Once every two or three days w/a low protein, high fiber diet.
This schedule is reversed in the spring starting w/low protein and increasing as the temps. rise.
Below 45 stop feeding all together. In the fall when temps. get around 65-70, I start mixing in some heavy proteins in the form of worms, krill, and other meaty items. This conditions the fish and allows them to get enough fat stored for a long winter. Fish will have always have something to eat in the form of algae or other micro-organisms when the feeding stops should the get hungry.