why ducks wont get into pond
Was the pond there before you built the pen around it? If it was there may be snapping turtles in the pond. We had this happen with our 60 mallards on our pond last year. They would not go in the water even if you tried to force them in and we did witness many attacks. There were two huge, 50 pound snapping turtles in there but we got them. This may be your problem.
Because as natural as it would seem, a grown duck that has never experienced water of that quantity and depth becomes overwhelmed. I have bought ducks many times from people who only had plastic swimming pools and when they finally get placed on a large body of water it scares them to death. Best thing you could do is take their plastic swimming pool away and they will eventually get used to the pond. Kacky has a point as well though, if there are large predators in the pond then they are smart enough to stay out of it.