I just came across what I thought sounded like a great idea for keeping a waterer from freezing in cold climates in unheated coops while using the kind of waterer I want to use: a hanging 5-gallon bucket with nipples in the bottom. The solution is placing a submersible birdbath heater in the bucket. They are more robust than aquarium heaters. I'd love to do this but in trying to find well-reputed bird bath heaters they seem to be either floating, plastic heaters (which is not ideal for a bottom-draining 5-gallon bucket) or made from aluminum. Aluminum is bad for chickens as it is for many animals. I wouldn't want to drink water warmed with an aluminum heater, so I'm not going to subject my chickens to that... Has anyone found a good submersible water heater that is not made from aluminum yet is still reasonably affordable? Thanks so much!