wrote:

Between my 198 watt swee****er blower, the 500 watt heater (or 2) and 110
watts for
my pondmaster 1200 gallon/hour pump, I am really eating up the energy
here. So I am thinking about a solar heater for my pond.

www.sungrabber.com has various configurations. They are made of
polypropylene (should be fish safe).

a wireless indoor/outdoor thermometer to tell me the temp of water and air
with a
remote switch to turn it on and off. I figure to set it up that the water
drains out automatically when the pump is turned off to prevent freezing
of water.

That's not a bad idea, but I rather doubt their _pool_ heaters are designed
as "drain-down" units, so you'd need to use the type they're selling for
domestic hot-water. Drain-down systems work for home heating, and are
generally pretty simple, but since people don't actually swim in their
swimming pools when there's snow on the ground, it's not a system that I
think they'd have bothered with on the pool heater (and it doesn't look
like a drain-down system). So I'd worry that when you drain it, it would
still have enough water inside to damage the collector.

For domestic hot-water use, we use a system much like Jan describes - a
glycol solution, continuously pumped through a collecter to a heat
exchanger. Since the pump is driven by a small PV panel (50W or less), it
only pumps during daylight (ensuring that you aren't _removing_ heat). For
DHW use, it doesn't need any controls at all - it can afford to keep
extracting heat from the collector forever. For a pond, you'd need a
max-temperature on/off switch - but then I'd worry about overheating the
collector.
--
derek