K&H Pet Products Thermo-Pond 3.0 Pond Deicer Black 100W The world's most successful and efficient low-wattage pond de-icer Uses only 100 Watts and maintains a hole in backyard pond ice for just pennies a day Floats on top of the water and is completely safe when used with a pond liner or plastic pond Fish friendly - assists the escape of toxic gases all winter long to help maintain a toxic-free environment for fish living under the ice Tested in northern Wisconsin at temperatures of 30 below zero Fahrenheit and is MET Listed