I have to use a 1 gallon plastic bucket to water my chickens inside of their coop this winter. It is a fairly small coop and I only have 3 chickens, so that is why I am using such a small bucket. I plan on using horizontal nipples and purchasing a cold weather thermo cube to plug the heater into. I just want to make sure I am not heating the water too much, I don't want to be giving my chickens 80 degree water, I just want it to stay above freezing. How many watts should I be using? I found an aquarium heater that only has 10 watts, is that too few? Thanks!