As no two seasons are the same, the safest way to regulate pond food is to use a thermometer to measure temperature, and then feed fish according to this suggested table:

Pond Water Pond Temperature Regularity Type of Pond Food (Never feed fish under Medication)
Below 10°C DO NOT FEED Below 10°C for more than one month may require feeding of wheat germ occasionally, especially smaller Koi fish.
10 – 13°C 2 – 3 times per week Per week if Koi are hungry High carbohydrates, low protein laxative-type foods. Wheat germ, squash, lettuce and brown bread.
13 – 15°C 4 – 5 times per week if Koi are hungry Wheat germ along with vegetables. Increase quantities gradually as temperature increases.
15°C Once a day, 6 days a week Wheat germ along with carbohydrates such as brown rice and vegetables.
16 – 18°C Once or twice daily Gradually increase protein value and quantity of food, and vary diet with fruit and vegetables.
18 – 23°C 2 – 3 times per day Bulk of diet should be high protein. Add fruit, vegetables, plankton and live foods for variety.
23 – 27°C Up to 5 times per day High protein food with colour enhancers. Add plankton, vegetables, fruit and live foods.