Mark,
I hope Bill or James or someone smart will respond as I am usually just repeating what someone with knowledge has advised before. I would suggest searching for posts on aeration.
If one is trying to maximize fish production of a pond it is usually desirable to maintain 18" to 24" vis which is acheived by fertilizing or natural run-off of nutrients. In this scenario it would be desirable to have & not loose aeration. I think if maximum fish production is a goal windmills alone would be chancy.
I'm not sure if loss of aeration would be as much of a concern if one does not have a fertile pond.
