Oh yeah, I presented my worry of the waterer freezing here earlier, here's what I decided to solve it with. Haven't installed it yet.

It's a self regulating heat cable meant to keep water pipes and gutters from freezing. Built in thermostat, just need to plug it in, and it should keep the water right above freezing temperature.
It's a self regulating heat cable meant to keep water pipes and gutters from freezing. Built in thermostat, just need to plug it in, and it should keep the water right above freezing temperature.