AQUASCAPE - 300 WATT POND DE-ICER is a floating thermostatically controlled stacked disc designed to maintain a constant opening in the ice so as to allow for gas exchange. NOT A HEATER - This unit is tough enough for a zone 3 winter and may be tethered in place prior to freeze & then plugged-in when ice forms. L.E.D. indicator lights let you know when then unit is heating and also a standard 'on' light to let you know that it is still plugged-in.
Best when used in conjunction with a good air pump diffuser system placed beneath the de-icer. These 2 components should be sufficient for most winter set-ups. A reliably filtered pump will enhance this winterization method as moving water does not freeze easily.