Greg Cooper wrote:
Ok I know that "Spring has sprung" and all - but my pond does get a lot
of shade and warms up slow.
I have wondered about the idea of a using solar heat from a roof top
collector to warm the pond to a better temp and extend the active season
for my finned friends. Not that I have actually done more than
thinking about it - living is coastal BC is about the worst place next
to Washington state for hours of sun shine anyway. But I thought if
nothing else maybe it would be an interesting thought experiment and who
knows maybe someone out there has tried it. I am thinking that one
would need a water/water heat exchanger because circulating pond water
up through a collector would grow algae and clog I am sure.
Crazy idea? what do people think?

Cheers.
I thought about doing this myself however the thing that put me off was
that solar heating would deliver during the day. The consensus seemed to
be that fish like slow temperature change. My pond already has a 2-3 C
temperature difference between day and night, and increasing this would
likely stress the fish. Some Koi people claim that anything more that
0.5 C, a day is stressful at least for Koi. However my pond gets lots of
sun so it might work for a shaded pond, you'd effectively be getting the
sun without the sunlight (and associated algae)

On the practicalities you could have a heat exchanger in the pond and
circulate your heat transfer liquid (presumably water with some
additives) and so not have algae clog up the system.
From what I read there are two main types of solar collectors, the
swimming pool type which are designed to raise a large amount of water a
relatively small temperature would be appropriate, there are some aimed
at domestic water aimed at heating a small amount of water but heat it
to high temperatures - these are probably inappropriate.

Thinking on the fly - maybe if you had a relatively small tank which was
well insulated, heated to high temperature, and then pumped that
liquid to your heat exchanger in the pond, you could deliver heat in
controlled way throughout the day and night. Sounds expensive though :-(
and you'd need a fairly sophisticated control system.

I'd be very interested if this turned into anything more than a thought
experiment.
Good luck
Peter