I've seen a lot of people who have problems with their horses pooping in their water buckets in their stalls, but since I've moved my horse to pasture board, he still poops out the water bucket out in the pasture. I'm sure his pasture mate doesn't appreciate a nice steamy one in his water.
Right now, the bucket is on the ground, and there's not really any place to move it up higher, nor is it even high enough now that he may be pushing his butt up to it, he's definitely just practicing his aim. I'm no longer amused that he's managed to potty train himself. Any advice?