In the colder months fish need a different type of food, as they move less in cold weather. It must be low in protein as the fish's metabolism slows down in winter. Wheatgerm is an ideal food for this purpose as it is low in protein and easy to digest, which also means it produces little waste.
Wheatgerm food is often supplemented with other goodies such as vitamins and minerals to reserve the fish's energy and health over the winter months and ensure that when the warmer weather arrives, your fish are in the best condition. Only ever feed your fish as much as they will eat, and remove excess food after a few minutes, this avoids a waste and toxin build up.