Here's what I decided to use, it's still sitting in it's package but I will have to take it into use soon:

It's a self regulating water line heater. Grounded plug, built in thermostat, doesn't overheat if the cable overlaps itself. It's meant to be installed in waterlines or gutters, but I intend to submerge it in my waterer. Don't know how well it will work yet, but this seemed like the solution that takes the least amount of work. It only heats the water a bit above freezing, so it doesn't use excess electricity. I'll try to remember to report back about how it works once winter sets in.
It's a self regulating water line heater. Grounded plug, built in thermostat, doesn't overheat if the cable overlaps itself. It's meant to be installed in waterlines or gutters, but I intend to submerge it in my waterer. Don't know how well it will work yet, but this seemed like the solution that takes the least amount of work. It only heats the water a bit above freezing, so it doesn't use excess electricity. I'll try to remember to report back about how it works once winter sets in.