I agree about the netting. I only cover mine in the fall/winter to prevent leaves from filling the pond once the skimmer is shut down.
I have had problems with Herons and Racoons so I installed a electric fido type fence using bamboo stakes with two strands of fence circling the ponds one about 6 inches and the second about 18 inches above the ground. The units are not expensive, purchased mine from TSC. The bamboo stakes are much better looking than the provided plactic stakes. Easy to install.

i saw in a foster and smith cataloge a thing that was a sprinkler with a sensor on it. when a preditor came close the sprinkler would come on and scare them away. they had several options for preditor controll. one was even an owl with a sensor that would hoot and turn its head. it was too cute that we got one just for the looks.

maybe if you look on there web site you will see some ideas.. good luck. laura

I have tried fishing line around and over the pond I have tried cds hanging from the trees and neither one of those have worked so I took my husbands turkey decoy that he used when he went hunting and put it near the pond and I havnt seen a bird insight all summmer but I do miss the little birds like robins and cardinals that used to visit..

We've had a heron decoy for years that seems to work. You just have to move it regularly.