Evaporation causes cooling that is faster than the direct conduction of heat
from the pond to the air. In southern Arizona, many years ago, we used
swamp coolers for our air conditioning. The water falling over a waterfall,
or tumbling down a stream, or being shot into the air for a fountain, has a
higher surface area than the pond, and therefore will have higher
evaporations than the pond alone. The pond will be cooler with the
fountain, stream or waterfall running than without. If the pond temperature
is above 50 degrees, then the fish should be being fed, and the filter needs
to be running if the fish are feeding. The filter should not be cycled on
and off. It will go anaerobic during the shutdown, producing hydrogen
sulfide gas which is very toxic to the fish, and the filter bacteria will
die back such that the nitrogen cycle is not taken care of. I know people
up north turn off the filter for the winter, and that is because of the
potential of freezing pipes in a power outage, or ice buildup at the
waterfall that can cause the water to be diverted from the pond. I
definitely would not turn off the filter unless the pond temperature falls
below 40 degrees, which is the temperature that the filter bacteria are
reported to die off.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"Gabrielle" wrote in message
...
I have a young friend who just bought a house with a small pond -- he
ignored it at first and then got porged. I give him some rosy reds and
he bought a dozen feeder GF. Now he's worried about their winter
comfort. We're in southern Arizona so they won't get too cold, but he's
still concerned.

Someone told him that running water is warmer than still water, so he's
been running his waterfall 24-7. This doesn't sound right to me, I think
running water is cooler. I've googled and asked Jeeves, but haven't come
up with a quick answer.

I think he'd be fine leaving it off at night, which is what he'd like to
do, especially since he does have a bubbler running separately.

Comments?

Gabrielle
in sunny Arizona where the air is 51F and the water is 49F.