In my experience no ONE defense is the answer. I often recommend a series of obstacles that in combination usually works. If there was ONE product out there that did the job, there wouldn't be so many inventive choices
I LOVE my motion detection Scarecrow!! It solved many problems with herons and coons. The trick with using them is to have a couple of them spread apart for herons. Herons move slowly so can sometimes "fool" the Scarecrow so if you use two (or more) you've got it covered pretty well. At least that worked for us.
I also have coons. A WHOLE family living right at the rear of our property in a large hollow in a big oak tree. Every once and a while, late at night, you can see them all in a line walking across the backyard, but since we placed the scarecrows to monitor the ponds, their path of travel is FAR FAR away from the ponds. My guess is, they learned
We also net the ponds, but any well respecting coon would simply rip that up in no time, but it does slow them down long enough to get a good dousing of water from the sprinkler.
Good luck Noonie!! The wildlife is very hard to deal with sometimes and I don't think there is a hard and fast protection out there. At least I haven't seen one that I would use. I'd be nervous about anything electrical around the pond for fear of either hurting myself, our dogs or stray electricity harming the fish.
UMKC 2013 Koi Show & Product Expo
August 10th & 11th, 2013