I heat my ponds and maintain near 70 all winter in Zone 7. If you are going
to try to heat, I would recommend that you keep the pond above 65 degrees to
stay out of aeromonas alley, or keep the temperature down below 50 degrees.
The heaters that I have are 1800 watts each. I have 2 of them on the 4000
gallon pond and 1 on the 2000 gallon pond. They are really the backup heat
source though. The ponds are covered with 2X4 lean-to shed roof of 2 layers
of polyethylene sheeting and a layer of bubble wrap. This acts as a solar
greenhouse and the temperature in the greenhouse on sunny days in February
will be near 90 degrees, but come the long nights the temperature drops and
it can lower the pond temperature 5 or 6 degrees if the lean-to is covered
with snow, preventing the solar gain. My heaters are from Aquatic Eco Cat.
# QP-20.

Unless you are extremely far north, I don't believe you could get the pond
to freeze all the way through at 4 feet. That would take a tremendous
number of sub-sub freezing days. The ice does need to have a hole through
it to allow gas exchange for the fish, and this is best accomplished with an
air stone mounted just lower than the bottom of the ice. A water trough
heater may be needed to help the air stone maintain an opening.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"Jerry Cloe" wrote in message
...
I plan on setting up a somewhat small pond (probably around 7500 gal's,
but
less than 4 feet deep). I realize that the surface freezing over isn't a
problem, but I'm worried about it freezing completely through.

I'll have a pump to generate a small waterfall (and will have filters
setup
at that point).

My question is should I install some type of small water heater or
something
and heat the water (probably set at 55 to 60) so as the temps start
falling
below the water will be maintained.

Does anyone have any ideas or input on this? Reading through past posts I
don't really see that much about heating.