Sissy, I did too, and still do when it get's really cold, first thing I do when I get up and it's -40 is put my boots on and run out to check pond, just to be sure.... you never know when it that cold, you got be be ready for anything. A few years back when my bottom pond was smaller, and I had a small pump, (under 400 gph) if the filter got plugged the hose would freeze, and when the pond quit flowing with the rest of the other ponds, it would freeze solid pretty quick, and I would have to work fast to get it flowing again before the whole thing would freeze to the bottom solid. That small pond always gave me trouble, as the small pond was the bottom pond and it would keep the other ponds "topped up". I did take it out and redid the bottom pond a couple years ago, making it much bigger, now I have no trouble as long as the "power stays on". One year I had to drag out the generators cause in the middle of the winter someone hit a power pole and it knocked out power for a few hours, had to drag out the generators and get the pond running, as long as it was flowing like the "creek", even though the heater in not plugged in, everything was fine for a few hours.
If your wintering your pond up here in the "arctic" keep extra hoses, pumps, filters handy, just in case, cause you never know......