Fish enter periods of dormancy called "torpor" during the winter. This reduces their metabolism and makes it so they need significantly less food in order to survive. Fish will either survive off the fat stores they've collected in the rest of the year, or eat small meals in the way of underwater invertabrates. Your fish will likely be able to survive without any additional food from you during the winter, as long as they've entered their dormant period properly.
Fish know when winter is coming by the slow reduction of available food in their environment. You can simulate this natural occurence by reducing feeding as things get colder in preparation. You'll want to reduce the frequency of their feeds once temperatures drop below 70 degrees, and halt feeding completely in temperatures under 50 degrees.
