I have been considering a few different options for water heaters. I know some use a heated dog bowl but those seem to run quite pricey. I was looking at some cheaper options and came up with a few things I have access to. Submersible Fish Tank Water Heater: http://www.petco.com/product/114078/Tetra-Submersible-Aquarium-Heaters.aspx?CoreCat=OnSiteSearch or http://www.petsmart.com/product/index.jsp?productId=12315584&f=PAD/psNotAvailInUS/No My only concern with these is they are intended to heat water to about 70-80 degrees. I'm pretty sure they dont have the power to take near freezing tempertures up to that but if only about 40 degrees is necessary, could it constantly runnning for not being up to temp casue them to burn out fast? Heated Cord: http://www.petco.com/product/109980/Zoo-Med-Repti-Heat-Cable.aspx?CoreCat=OnSiteSearch I dont know what temperature these will run at but could these work if wrapped around a watering can or bottle? Heated Pad: http://www.petco.com/product/6353/Z...-Under-Tank-Heaters.aspx?CoreCat=OnSiteSearch I think this would generally work for waters, not sure if this might also get too hot. If you have any recommendations or know that something definitely wont work or will cause problems, let me know, I am planning on going to morrow to a pet store to find something.