Treats for Ducks?

i have tried feeding them in the pond, but after a few  of hens fell in (pip was poised ready to go in after them, they did get out themselves after a lot of flapping and squawking) we decided it wasn't a good idea, they have their food in a cat litter tray (new) in the cowshed, it's just a case of finding something the hens don't like, so that when we do a roll call the ducks can have something too.