Pond heaters are essential kit in the winter months. They are designed to stop an area of the pond surface from freezing over to allow oxygen into the water and to let toxic gasses escape from the pond. Vegetation and waste matter will cause toxic gas in the pond which needs to escape and these pond heaters are designed to allow this. In the summer, aquatic plants produce more oxygen but in winter your fish need to take their oxygen from the water so it is vital your pond is kept from freezing. We also stock heaters designed to gently warm koi ponds all year round.