We live on 18 acres in the country and have a small pond (about 100' x 100') that is about 8 feet at the deepest point. There is also an island in the middle. We have 12 ducks that live on our pond. My concern is predators being able to cross the frozen pond and attack my ducks. What is an inexpensive way to keep the pond (or large sections) from freezing, and having predators able to walk on it. Thanks for any advise you have (and my ducks appreciate it also!).

P.S. There are NO fish living in the pond.