IRISCOTTAGE.
Try making the Greg Bickal Deicer, its cheap, works great, only uses two light bulbs and one can add an air hose if needed.
Depending on the size of your pond you can make it in various sizes.
First a Floating platform, usualy 2 ' PVC. Then a Container(from wal mart etc" inside mount two light fixtures on the Roof(inside) not too close to the plastic, then if U wish the air hose.
I have been using them for about 6 years. Low on watts, and has never failed me, even at way below Zero. I can send pictures if U want.
RichardK.