Herons, egrets and other fish-eating birds love to see a pond being installed in a garden because they know that fresh fish will be on their menu soon. Nothing is more frustrating than walking outside to sit and relax near your pond and find an huge white egret having a dinner of your largest goldfish. Although the great white birds are beautiful and elegant, pond owners would rather they ate elsewhere.
There are several ways to deter egrets and herons. Stringing fishing line just at the surface or just under the water of the pond will keep them from getting in the water without tangling up their feet. This is an effective way to deter the fish eaters, but does get in the way when you want to feed lilies or clean out the pump.
Putting a Gator Guard in the water is one of the most effective ways known to deter herons and egrets. His eyes glow and follow the egret around. The Gator Guard is about 30 inches long and can detract from the appearance of your pond. He is very realistic and as ugly as a real alligators.
Throwing a big piece of black netting over the pond can be very effective for the same reason as the fishing line is. But the black netting is just as ugly and gets in your way as much as the fishing line does.
Using a scarecrow motion activated sprinkler is an extremely effective method to deter birds. It emits a 3 second spray of water the moment it detects motion around the pond. The only drawback to this method is that you'll sometimes forget the sprinkler is there and get a good 3 second soaking yourself.
Placing an inflatable owl next to your pond has worked for some people, but not all. It's worth a try.