As the water temp goes down, so too does your fish's metabolism. They require less as that's the way they're designed to survive. You can still feed them as long as they appear to be eating, but sparingly. Any food not eaten in a five minute span should be taken out of your pond. It's natural to worry, esp the first winter, but fish have been doing this for a lot longer than any of us have been alive. Once the water temp (not air temp) hits 50, I stop feeding altogether. If you can see algae on the sides and rocks, it should be enough.
As long as light can penetrate the surface of your pond, the algae gets what it needs to keep on reproducing. Hence why it's a good idea to shovel any snow off the ice after it forms, but that's to keep ideal winter conditions. Even this isn't necessary as long as your fish load is low, your organic debris at the bottom of your pond is light, and a hole is maintained for any gases to escape.
Hope this sets your mind at ease.
Michael