Hi cmfulmer ~
I don't think a windmill would give you adequate dependable aeration - they are good for small ponds under an acre, and even then only if there is enough wind. When you need aeration the most is during those hot still summer days. They do look cool and surely have their place, but if there is any way you can go with electric I would definately recomend a properly sized electric system. Do you have power with in a few hundred yards?

Sue Cruz
Vertex Water Features
www.vertexwaterfeatures.com