"Bill Stock" wrote in message
...

I did some measuring today and I only seem to have 24" of depth, so I'm a
little concerned that the bubbler won't do it. I could swear I had 30"
(must
be old age ), but I'm not sure I was hitting bottom either. The netting
was obscuring my view. The plan is to set up a temperature sensor about 8"
off the bottom and use the deicing cable to maintain a 40 degree temp. I
don't really want to heat the water, just keep it warm enough to prevent
fishsicles. Do you think 300 watts will be enough if I cover the pond?

Water is densest at 39 degrees. The soil under the pond will be pushing
heat to the bottom of the pond. If you use a heater, the warmer, 39 degree
water will fall to the bottom. If the water warms above 39, then the warmer
water rises toward the surface. If the surface is frozen, then you are just
creating a circulation of bottom water toward the top, until it reaches 39,
and then it will fall to the bottom again. The ice on the surface of the
pond acts somewhat as an insulator, making it more difficult to make the ice
thicker and thicker, and with the bottom contributing heat, the pond is
likely not to freeze completely to the bottom, though pond depth, and
location can result in completely frozen ponds.
--
RichToyBox
http://www.geocities.com/richtoybox/index.html