I have a small plastic kiddie pool I dump every day or two. Just easier and cleaner. I also have naturally running water on the property which helps tons. With all the rain this year the kiddie pool stayed empty most of the time.

I don't have a frost free faucet outside so for all my livestock I have to drag the hose in and out of the basement all winter. For the dead of winter the ducks just have to make do with a big rubber feed bucket filled with water. The rubber makes it easy for me to smash out the ice and refill.
The nasty water isn't healthy for you or the ducks. Great for dumping on your gardens though. It's sewage, ducky sewage but sewage just the same.

I have 4 ducks, and I also keep a little plastic kiddie pool for them and change the water everyday because it is better for them. So I would suggest getting maybe a couple of them. Ducks love swimming and it is really easy to just dump the pool out every mornig and fill it and just do that every day or so because they love the mud that you mske when dumping it out and then they love swimming in their new clean pool.

This is funny because I have two large natural ponds connected by a creek and those ducks keep the edges nice and clean of all the little weeds. When they go plop in my ponds the fish quickly eat it up!I once read that Tilapia raised in China usually are done on a duck farm and they shovel the duck poo into the pond for the Tilapia to eat. Guess who buys the Tilapia t restaurants?