Stainless would be a better investment.  My plastic ritchies are coming out as they fail.  The donut in the water idea is a pain to manage.  All mine need heat underneath and those heaters have to be babysat.  Hard to beat a solid steel fountain with enough reliable heat under it that you don't have to worry about it every cold day. The red Ritchie lids fail from the sun.   Check out Everlast fountains made in Hull IA.