Well......If your up for some input....
This is a battle that has been fought for a long time, an insulated trough, (tough enough to withstand animal shenanigans) is far easier / smarter / on the pocketbook than constant power input.
What power input you do spend can be minimized by simple physics....A; heat rises, B; exposure to air is all that required for aeration.
With the caveat that Its better to hydrate animals with adequate quantities of
water, than to give them an inadequate supply of "fresh" water!
So.....to my simple mind a double walled trough with at least eight inches of insulation between two animal tough shells is the best start, then a simple 4" stainless tube passed through within 2" of the bottom, with caps, to contain 2 60 watt halogen bulbs in series for heat.
(Halogens create an extraordinary amount of heat for wattage input, wired in series they last forever because they are so far below their max power constraints, they are available cheaply everywhere!).
Aeration is accomplished via simply rolling the water from bottom to top because .....heat rises! But if you wanted a more dynamic aerator then put your heat source at the bottom of a "percolator" arrangement.
But!!....... the hotter the water the faster the evaporation, And!....the more water is exposed to air in the processes of aeration the faster the evaporation....so unless its attached to a float valve with a constantly on source, perhaps moderately stale water is preferable to clouds of steam building rime frost....
