Esther is right about knowing where you live, if you don't mind sharing that info it is easy to update your profile with at least the state and or your tempate zone.
Like Esther we turn our pump off for the winter, not only does it save us money on the electric for a few months, but we don't have to worry that ice may form in an area and divert the waterflow out of the pond, nothing worse then loosing water in the winter. As for O2, colder water holds more and the fish are in a sort of state of lethregy and they do not need as much. We use a small pump about 250gph set about at the mid water level and just enough force to just wiggle the water so it does not freeze in that area, leaving an opening for gas exchage. This year I think I will also try to build the totebox heater so many ponders use, I've had the stuff for a couple years just have not gotten it built. Put in your deicer, bubbler pump, totebox heater etc. before the ice is on the pond. And never pound on the ice to break it, boiling water is a much better option.
