I would put it over their food instead of in the water if it were me.I was thinking about the waterer this morning when filling it... guess I’ll give them a bucket later so they can really go crazy!
I was sent home with some brewers yeast the other day and instructed to put it in their water too....
I’m not really set up for ducks, so these cute little monsters are probably going to my sisters house as soon as the cute wears off ...

I *think* it's something like 1 tablespoon to every 2 cups of feed if I remember right. I don't usually use it because the feed I use seems to have enough niacin.