Bruce, Cecils method works well and Carys comments are right on track also. If you dont want to install a diffuser in shallow water a deicer will work just fine, Both serve the same winter purpose. I use a Koender windmill airstone and supply .5 -1 cfm to it.Installed in the far end of the ponds. I seem have a ton of them and they dont circulate much water so they are a great winter device or a summer "beach scrubber" for the recreational ponds. Another device to look at for this and other purposes is the WG Airpod from Aeration Technologies Inc.Ted