Ingrid,

Did you 500w heater run full time last winter? I noticed that you said you
had 1600 gallons, about half of which was above ground. Yet your 500w heater
managed to keep the pond above 50F, except for two months.

I bought a 300w heater, as my pond is less than 500 gallons and completely
below ground. Although I only have 24" of water, the actual hole is about
32" deep. I plan to keep the bottom temps around 40 in the cooler months,
but may experiment with keeping the boys above 50F in October.

I'm just not sure that 300w will be enough. I wanted to test the heater, so
I stuck it in a bath tub (45g) at 60F with a powerhead for circulation.
After 7 hours, the temp was only 84F, while room temp was 70F+. Granted the
tub was not covered, but I was hoping for better. Although the room was
getting a little humid. How susceptible are these heaters to burn out if run
for extended periods?

If nothing else, I've got a cheap Jacuzzi.