What do you guys do for water for your ducks? In the spring/summer/fall we have a "pond" in their run that the love to swim in. We dump it every other day and it stays pretty manageable. But here in the NE we are now below freezing during the day and night. If i put a smaller water trough in will they still try to swim in it even though it's really cold? how can i keep the water clean and defrosted??? thanks!