Well, this past summer I completed a large pond project for a customer (30K Gals - two main circular pools interconnected with large boulder stepping stone bridge, upper fountain basin with spillway and stream, 12ft waterfall), and the last thing I did was throw in 36 cheapie fish so they'd have something to look at....I didn't bother planting the peripherals and lilies due to the lateness of the season and lack of selection up here.
I went back a couple of days later to complete some flagstone and asked the lady if she was enjoying watching the fish........she said "Fish?, What fish?".
Sure enough, no fish. Heron scooped them all out in one day.
I installed a motion-detector jet sprinkler for her. So far, so good. I'm not fond of the look of netting.
When the snow melts (if it ever does), I'll post pictures of the completed project. I didn't take any photos in the Fall.
In my own pond, I've had problems with racoons in the past, you can tell when they've been around because they leave land-mines everywhere they go. Oddly enough, I've lost fish to racoons, but they haven't eaten them, just chewed them up a bit and left them in the garden to taunt me. Have I mentioned that I don't like racoons?