I use those plastic ones with the red bottoms for my baby chicks but as they went into the coop at 8 weeks they graduated to the black rubber tubs used for stock I think? They come in several different sizes and can't be knocked over. they are open and the chickens have plenty of fresh water. I also use them in my dog pens. I just carry a pail of cool water to refill them and not carry the tub at all. Hope this helps. Love the idea of freezing blocks of ice for summer.