what is the ideal type of feeder for ducks?.. the chick feeders work great for a while, but our older two ducks have difficulties eating out of that type of feeder...we tried giving them a couple different types of chicken feeder we have laying around, but the feed gets wet and clogs the feeder so nothing comes out... we have resorted for now to a simple dish of feed, but they make a horrible mess and waste a good portion of it... what do you folks use?...