Years ago when we had cows, I got tired of dinking around trying to keep the tank from freezing up, or chopping ice.  We had a 100-130 gallon galvanized tank with 4x4 posts and a frame around the tank. I took all the sawdust/wood chips out and got 2 long strips of heat tape. I wrapped the heat tapes around the outside of the tank using duct tape to hold the tape on the side of the tank I brought the electrical plugs so they were accessable and only visible from outside the corral.

I then refilled the space (4-5 inches) carefully with the sawdust/woodchips and put a plywood top on the tank nailed down well to the wood frame on the outside, cut out the inside to the inside edge of the tank.

Worked fantastic, Cows always had access to warm water. Wasn't "hot" just warm so I could put my hand in the water in the worst cold and not be cold.  Cows Loved it, they did MUCH better throughout the winter having access to warm water. Didn't matter if the Temps got to 20 below Zero, water was warm enough to drink !

My "homemade" water heater worked for over 10 years and never ONCE had any issue about "fire" etc. There were thermostats on the 2 heat tapes.

Downside, need electricity and electricity did get expensive.  Only physical issue was I leased the corral to a guy few years ago to winter his herd, and wanted to "clean out the corral"..  Despite specific directions, "Do not run into the Water tank with the tractor loader", sure enough he rammed in to the tank a couple of times and screwed the whole thing up.  (grrrr)

He never believed Cattle needed access to warm water in the winter, but he did say his cattle "seemed to do better in your corral" during the winters.