FrankS,

You might consider a procedure the Japanese use on their ponds where the
winter is severe. They place boards across the pond at the appropriate
width and frequency and then use the boards to support bales of hay covering
the entire pond expect for one small area at one end for gas exchange.
Barring this technique, you may want to consider using Styrafoam sheets,
like the ones used on the side of new construction homes. I presently have
one shutting off my back porch where I have extra tubs with fish in them.
You would have to figure out a support mechanism for snow weight and
probably for weights used to hold the sheet(s) down, and you would still
have to leave a small opening to allow for gas exchange, but it has worked
for me over the years when I deemed that I needed it.

HTH

Tom L.L.
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"FrankS" wrote in message
...
I live in North Dakota and for the last week or so the temperature has
been
VERY cold. The night time temps have been as low as -28 degrees F for
several nights with the daytime high temps staying below minus 10 degrees
for about a week now. This is cold even for us natives.

I have a small pond, about 300 gallons, stocked with gold fish, a comet,
koi
and shibunkin(sp?) and maybe a crayfish or two. The pond was nearly
covered
with snow and frost that I was sure the fish would be crispy critters by
now
but this afternoon I braved the cold and went out to check on them. I was
surprised and, to say the least, pleased that everyone seemed to be in as
good as spirits as possible under the circumstances. I use a 1200 watt
floating stock tank heater and a bubbler pump but I wasn't sure if the
heater could keep up with the constant cold temps. This, to me, is proof
of
the hardiness of pond fish and the value of a $30 heater. My real
problem
is evaporation, the cold air is very dry and the comparative warm water
makes for rapid evaporation so I'm the only guy in the neighborhood with a
garden hose stretched out in the back yard all winter.

Anyone have a similar experiences?

Frank