The Laguna 315 watt heater/de-icer will keep a hole in the ice on otherwise frozen ponds. Since it only uses 200 watts of electricity, it will not even be noticeable on your utility bill! Keeping a hole in an ice covered pond is critical to the health and well being of your fish. The hole will allow oxygen in, and poisonous hydrogen sulfide out. This gas builds up as any organic materials break down, and it needs to be able to escape the water thru the surface. Without this hole, it is just a matter of time before the fish are poisoned.
See our Wintertime Health Risks article for more details