That is a very small volume of water to get fish through the winter. Do you actually have fish in it now? How big are they? You may want to consider bringing the fish into an aquarium setup if you already have fish. I imagine the fish are not that big yet coming from such a small outdoor setup. You won't have to spend all that money on heating up the water if they are goldfish. They will be fine as long as you keep your home at 60 degrees or warmer - you can even keep feeding them through the winter then. Other than that, if you don't have fish in it yet, it may be easier to just drain the pond for the winter. Just my 2 cents.
It makes it difficult to give proper advice. Just need to know the north or south part of the state or country. If someone feels the need to keep such general information private, it would be better not to ask questions and just read, their question will come up eventually from someone who can.