Managing Pests and Predators
Most homeowners like the idea of a pond teeming with wildlife but there can be too much of a good thing. The cheerful sound of three or four chirping frogs turns deafening when hundreds of tadpoles grow into hundreds of adults.
Adding one or two predator fish can control tadpole numbers and keep insects down too. A largemouth bass may not be as pretty as your vegetarian Koi but the two species can live together as each does its own job.
Protecting Your Fish Then there are the predators that prey on your fish. A heron perched next to the fishpond looks beautiful and graceful---until it eats your most expensive Koi. Fortunately, herons are territorial so a decoy can work here. If it's big enough, your heron decoy will look just as pretty and keep the hungry ones away.
Raccoon can also terrorize fish. To discourage raccoons and other predators, give your fish a deep enough well to escape wading animals. Construct hiding places with large shelves of flagstone, submerged pipes or faux rocks designed for this purpose. A "scarecrow sprinkler" is another option. These motion activated sprinklers surprise predators (and hungry deer) away.