The Superfish Pond Heater is a vital addition to your pond in the cold winter days. When the surface of your pond freezes over, the Superfish Pond Heater keeps a vital hole in the ice to allow the necessary exchange of oxygen and gasses between the water under the ice and the air above. This heater is not designed to raise the temperature of the entire pond like products such as aquarium heaters, rather it keeps a smaller area of the water warm immediately surrounding it.At only 150 Watts, the Superfish Pond Heater is also very energy efficient. It has also been tested in temperatures down as low as -20 degrees. Specifications Power: 150 Watts Cable Length: 5 meters Dimensions (LxD): 25cm x 24.5cm Comes with a 2 year manufacturers guarantee