Since your water is hard then you no doubt have Chara. Bottom aeration will not produce any negative impact on Chara growth. Since copper compounds are not feasable then Aquashade, Grass carp and removal are primary choices. Since you are in WI grass carp are probably not an option for you. I am not a big chemical proponent, but I think there is a non copper formulation that you could use. I will check into it. Kelly Duffie may be able to give help on this.
There is a pond/lake mgmt company in WI that is good and quite knowledgable but as far as I know, they do not frequent this forum. If I were you I would call them to see whay they say about your situation. All you are out is a phone call: Aquatic Biologists Inc 414-355-5346.
