Ah propane and propane accessories. No reason not to use it to heat the volume up. My parents house in NorCal use propane for heating and cooking. No matter what the fuel is available, mom still manages to burn dinner once or twice, she has cooked on wood stoves, electric (managed to melt a pan onto a burner) natural and propane gas.
check out this idea to heat your pool
http://members.cox.net/toddharrison/...ter/index.html 
something on a smaller scale could be done to use the flue heat that is currenlty not tapped for use. I'm thinking something more in line with a foced air heater