I visit a "pond" group, periodically, as I'm a pond "wannabe". Some of the folks, there, have had problems with predators, including cats, racoons, Herons, etc getting to their fish. Many of them have done some elaborate electric fence type designing over the edges of their ponds to keep the predators out. I guess if the problem is bad enough, that might be an alternative. I'd sure try the less expensive, less unsightly methods mentioned by others, first, before going to that extent.

I wish them luck!

Logan