I put my aquarium heaters in 5 gallon buckets with the lid on, and plug them into thermal cubes so they only come on when it's cold out.I always think that the problem with an aquarium heater is it
1. Heats the water, usually you only need the water at 35 or 40F. So, that is extra electricity waste, thermo cube or not.
2. They bust when run dry.
3. They are not sturdy. So you wouldn't want to put one in an open water bucket where birds could peck it.
That is why I like the de-icers.