Pond Heaters
Just a quick word about pond heaters…
you don’t really need them, but they could be convenient to have. All you should do during the winter is make sure you keep a small opening in the ice to allow gases to escape. This is only if you have fish in your pond.
The best way to do this is to have just a small air stone going and if your pond should completely freeze up, pour some boiling water on it to open up just a small hole. Whatever you do if you have fish, don’t beat on the ice to open a hole, you’ll stress them out.
I know it’s a little late in the season (March 2005 at the time of this writing), to tell you about pond heaters, however, take note and remember this for next year.
I live in Ohio and believe me it gets cold here; your fish will do just fine without the heater. In the 15 years that we’ve had our pond, we've lost only two fish, and it wasn't because we didn't have a heater for the pond. As long as your fish have plenty of room toward the bottom of the pond, which is where they will go during the winter, they'll be just fine.

Backyard Pond Tip