I can always tell when my ducks have visited one of my chicken pens. The water is brown instead of clear. 

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So, you do this on top of providing them with water deep enough to dip their head and nares?Since this hasn't been mentioned I'll bring it up. If you are worried about them running out of water or chickens getting clean water you can use a nipple waterer. In my coop I have two nipple waterers and several buckets. My oldest ducks were not introduced to a nipple waterer until they were older but had no problem learning how to use it. The open buckets get tossed and refilled daily and the nipple waters as needed.
The nipple waterers were a real life saver with the ducklings I'm currently brooding. Before they were big enough for the smaller buckets I used the old hole in the lid of a plastic container trick. Even with three containers they drained the water before I could get home from work to refill it. With the nipple waterer I knew they always had water to drink.
That’s right. In the coop they have multiple buckets in various sizes. Outside there’s tubs and a kiddie pool. Sometimes the water in the buckets gets pretty low because even with swimming water the ducks like to play in the buckets. They can’t get in the buckets but they splash a lot of water out.So, you do this on top of providing them with water deep enough to dip their head and nares?
I just had a long work week and didn't have time to do my normal routine. My ducks waterers were disgusting. I felt kind of bad - even though I provide them with a fresh tub of water every day.