I've been putting two 1/2gallon plastic juice bottles of ice in the 3 gallon metal water fount that is outside in the run. It will keep the water cool to cold during the worst of the heat(over 100 degreees). I put only one in the fount that is in the coop as it is in the shade. They stay pretty clean and only need a quick rinse and light sanitization before they go back in he freezer for the next day. We've been having a record dry and hot summer here in eastern Colorado and it seems to be helping a great deal.