At 45�14'N I suspect I'm further north than most members and I had a windmill aerator going during the winter to keep a 3' hole open even during -35C temperatures. However, last year I installed a geothermal heat pump into the pond and determined that the cooling effect of the aerator would work against the GHP efficiency.
I posted an update about my project at
this Pond Boss forum with some pictures of my aerator running in winter plus a followup after installing a GHP with the heat exchanger in the pond.
Our energy costs were $1700 less this past year than the previous year after replacing the oil system with the GHP. Not only was the quality of the heat nicer in the often -30C temperature, but we got A/C in the summer.
The windmill aerator runs when there isn't ice (Apr-Nov) and does a great job of keeping the water clear. Perhaps it is because the heat exchanger creates convection currents, but I don't see any difference in water quality with the aerator off in winter.
