During the cold Winter months you will want to keep a hole in the ice to keep your fish happy and healthy. Having a de-icer will keep a hole in the ice which allows harmful gases to escape. Having an aerator running, with an air stone half the depth of your pond, will provide your fish with the necessary oxygen they need to survive.
We strongly recommend that a pond de-icer be used with an aeration system, especially if you have fish larger than 8 inches. The combination of both make for very happy and healthy fish!