Hey Mark C, its been awhile.I dont remember if when you bought your windmill you had them ship it with the 7 inch stone or not. If yes and you are not using it (arent you using a CoActive Airstation ?)then consider placing the stone in about 2 ft of water as they make great winter diffusers.If you dont have the stone then go another month at best or until average depth is at or around 45-50 F and you wont need any aeration for some time.I switch our windmill in the display pond from the AirStation to the airstone the first week of Nov as a rule and shutdown the electric system at the same time.73 F air temp today so will wait a little longer this year perhaps.I would not be concerned about the airstone inshallow water this winter unless it was keeping the water open and temps remaimed 15 F or less with zero nights and the pond was 1/2 acre or less. The size of the pond is important.Everyone with windmill aeration and aeration in general remember that often neighbors, children and pets dont know that there is potentially "THIN ICE" Always weigh the RISK when considering winter aeration as fish are just fish !!