I have a 2 acre pond being dug as we speak in Indiana. What i need to know is if i need aeration or not for bluegill, F1s, redear, and baitfish. I would like to get maximum growth possible, and keep my pond free of excessive weed growth. Would one windmill be sufficient, or should i have two? Would i be better off by going with a fountain or diffuser type system rather than windmill(s)?

You will receive several view points on aeration in every situation. Info that would be helpful for figuring things out will be shape of pond, depths, and fertility of the bottom sediment. Diffused air from an electric motor(piston, or rotary vane) will be your best option for deeper water. Windmills are for specific applications(no power available,primary goal of keeping fish alive over winter, and places exposed to constant wind). Fountains are only efficient in shallow areas. You can save a bundle by doing it yourself from some of the catalog companies mentioned on this site. Do your research on some of the other posts on air, and remember you can't aerate too much during summer, but be careful during the winter. If you can get someone with knowledge to come out it is money well spent.
Robert B

Based on pond shape it will probably take 3 or 4 windmills for two acres. Get electricity within 100 to 200 ft or closer when building the pond. Use a 3/4 hp rotary vane compressor with four diffusers for 2 ac.