My first question is how deep is your pond? If it is above the frost line for your area (for my location, its 6 feet) I would suggest bringing in the fish. I keep mine in a cow tank I got from the local farm supply store in my garage along with a filter. It keeps the water above freezing, without having to worry about a heater. If you don't want your fish to go into hibernation mode, putting a fish tank heater into the cow tank works great. That's what I do. I haven't lost a fish in two years using that method.