Que the “Jaws” theme song. Herons, raccoons, and other predators like to hunt in ponds. This can cause your koi fish to hide more often out of fear of becoming fish food. One of the best ways to protect your fish is by installing fish tunnels or caves. You could also install a motion-activated sprinkler and put it near the pond. It’ll spray any predator bold enough to try fishing in your pond, including cats. Of course, this isn’t a permanent fix because, after a while, predators will realize it won’t harm them.