I have an idea that I am trying that I would like to share with the board. I am using an aquarium heater that is submerged in bucket for keeping the water from freezing. The temps last night were 10 degrees here and when I checked on the water this morning, the girls were drinking from the bucket. I stuck my hand in the bucket and the water isn't warm to the touch but evidently warm enough to keep from freezing. I think as long as the water level stays where needed, it should work great. Most aquarium heaters need to stay submerged or they can burn out. Let me know what you folks think...thawing and refilling water twice a day gets old and I had this idea that I thought I would try.