Xena's babies have an affinity for water tanks. It's all fun and games in the summer, but they climb in and destroy the tank heaters all winter long. I swear I've gone through more than a dozen with these two fillies in 3 years! We tried putting a VERY tough grid piece with bricks under and somehow even that got pawed out. I use rubbermaid tanks with the heaters that use the drain plug. Anything loose will quickly become a toy. Is there any cage type device for the heater that will stand up to a horse determined to destroy it? Hubb is frustrated enough that we are having divorce-level fights over how to not go through a heater a week. He wants to weld a steel cage but not attach it to the tank - which just means a metal object to poke, scrape or cut the horse when she gets it tipped over inside the tank. 

What about elevating the tank high enough to discourage them from getting into it?

Or...

I have a two year that likes playing in the water tank. I put a small one out for her as a "sacrifice" to keep her out of the main tank.

These are giantess fillies!! They are all legs and step right in to a 150 gallon tank. If I lifted it enough to keep her out it would be too tall for her sub-15hh pasture mate!

I am looking at a heavy duty heated silicon pad for under the tank. It is twice the price of a heater, but considering how many heaters we've gone through I think I'm fine with that, if it works. I don't need warm water, just no ice.

Ha! Yeah, I have little 14H cowponies so just setting mine on blocks discouraged playing in it. 

Hope the heating pad works! 

let it freeze.  They will make a hole large enough to drink from.  

But . . I live in a very blue area . . and I've been turned in for 'blankets' on my horses in the summer multiple times over the years. My luck is someone would turn me in for NO blankets on most of my horses in the cold, AC would show up, no water heaters might not go over well. I do break ice until it refreezes between feed times and then finally plug in. They do drink more when the heaters are on at least 12 hours a day. 

Is there any potential to use a heated waterer like the Ritchie brand.  I have those and they have an element (inside the unit) that keeps water from freezing.  Seems like mine would play (not as bad as yours sound) if they had a tank, but have never bothered the waterers...maybe because there is nothing to climb into anymore.  It would require an underground water line and electricity in place.  However, once in place they are basically trouble free only require cleaning out occassionally. Mine came with the property I purchased in 2008 and are still trouble free.