If you have a space in your water fall area could you just pop in a cheapy horse tank heater. At close to 3000 gallons your not going to raise the tempature much but maybe just enough to keep that thin sheet of ice off. Not that that should cause much of a problem though.
The heater would also keep the water from freezing up on the boulders around the stream, making it look nicer imo. I also think that the stream is going to be where you have more heatloss. As it will just change out the top layer of water that acts as a low grade insulation.
The heater would also keep the water from freezing up on the boulders around the stream, making it look nicer imo. I also think that the stream is going to be where you have more heatloss. As it will just change out the top layer of water that acts as a low grade insulation.