Pond de-icers are often confused with pond heaters. Even though pond de-icers and pond heaters differ, they both are responsible for keeping a small opening thawed on your pond's surface. This unthawed area in a pond's surface is important to let toxic gases escape and oxygen to enter simultaneously. Floating pond de-icers, unlike heaters, can keep the entire surface of a pond thawed because they float on its surface. Pond de-icers contain automatic thermo-regulators that turn on whenever the water temperature drops below 40 to 42 degrees Fahrenheit. Pond de-icers are used in small backyard ponds smaller than 35 feet x 35 feet. Pond de-icers range from $50 to $70 online.