Thank you. We did turn off the water bell. I am going to buy a large airstone
today and put that into the pond to keep it aerated well, over the winter.

V

On Tue, 25 Nov 2003 00:25:32 GMT, "RichToyBox" opined:

Turning off the water bell and the water fall from the small pond will allow
for all evaporative cooling to be limited to the rather small surface area
of the pond, rather than the large surface area of these. The heater can be
used to keep a hole in the ice, as can an air stone, or just the pump
without the water bell, just stirring the surface. Unless you cover the
pond with some form of plastic tent, greenhouse, or similar, the heat loss
from evaporation will be more than a heater can overcome.