My girls mess up their water so fast! Sometimes they fill it with wood shaving, straw, or sometimes they poop in it. I just clean it out every few hours.
Clean it daily? it'll never stay 100% clean unless it's low refilling it numerous times of day is a waste of water and time. In warmer times mine gets filled with mud lol Again, i refill every morning. Clean water IS important but keep in mind these are ducks not people, so you don't have to get carried away.