Do they still make those pond mills that sit in a pond to keep the ice from freezing? We have seen parts to some at farm auctions..but don't see any "on-line" for sale at any farm stores. We have a concrete waterer in the pond dam...but we are still concerned that cows & calves will walk out on frozen pond if some of it is not open for drinking. Our other option is to fence...we don't want anything to fall through the ice this winter. We're wondering what our best option would be. This is our first winter with cows & calves...hoping for a good experience.