We've gone through a few light frosts here recently and I have begun to think about how I will prevent the water from freezing over the winter. Are there any methods that I could use? The duck pen is far from the house so anything involving electricity is not an option for me, unless it's solar. I was thinking about getting a large black stock tank with a ramp leading up to it. Hopefully the large amount of water would hold some heat and the black color would warm it up a bit. The ducks would also be able to swim, which is a bonus for them. Though I don't think that this alone will do the trick. Are there any worthwhile methods of insulating a tank? If anyone has any creative (and preferably cheap) methods on how to keep the water from freezing, please let me know.