Thermo Pond, Pond Heater, by K&H Manufacturing. The world's most successful and efficient low-wattage pond heater. Uses only 100 Watts. Maintains a hole in backyard pond ice for just pennies a day. Can save up to $30 to $50 a month in electricity compared to "stock tank" style heaters. Pays for itself in two months! Floats on top of the water. Thermostatically controlled never to get hot. 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. One-year limited warranty. The second picture shows that ice will typically form up to the sides of the Thermo-Pond™. It will not harm or "crush" the unit. There is water under it which allows toxic gases to vent through the hole.

The final picture shows the hole created by the Thermo-Pond™. The best thing to do is to leave your Thermo-Pond™ in place. Don't move or disturb it during the winter.