Works against herons and cats and also protects against the theft of your valuable fish. More importantly it helps to keep children safely away from the pond. The pond alarm gives off a powerful acoustic alarm when uninvited visitors are nearby which shuts off automatically after 20 seconds. It is easy to install around a pond with a maximum circumference of 60m. With the optional obtainable set of 4 extra standards, you can protect 100m circumference. The pond alarm is watertight and works non-stop for approximately 14 months on the AA batteries provided.