During the winter, gases from fish waste and decomposing matter can build up under the ice and create a toxic environment for fish. This Pond Breather moves water above the ice layer to exchange the harmful gases for fresh oxygen. And instead of just keeping a small hole in the ice open like most de-icers, the Pond Breather is designed to freeze into the ice completely. A small stream of water is then pumped above the ice to the top of the gas exchange chamber where it mixes with air as it splashes back down within the chamber. Just enough heat is added to keep the water flow open inside the exchange chamber. This process allows the harmful gasses to escape the frozen pond, keeping your fish healthy. It aerates more than 4,000 times the water surface than pond de-icers on a daily basis. The Pond Breather creates a gentle current that moves oxygen through the water. It extends 8" above the ice to counteract doming, and 13" below the ice. Works in ice as thick as 15". Safe from power interruption - the Pond Breather thaws itself and restarts in a short time after a power outage. It operates at an energy-efficient 40 watts. 120 Volts, 60 Hz. 15-foot cord. Pond Breather uses 31 times less energy than 1250 watt pond de-icers L 8" x 8" X 22.50"