Hi Hartfish ~
7k for a 3.5 acre pond does sound a little on the high side. I would recommend a second opinion....
Under-aeration in my opinion and experience is worse than no aeration. When you under aerate you mix the water without getting the oxygen levels where they need to be, so you are basically mixing the bad water with the good water and making it all bad.
In your situation, though, I think you may have been quoted more than you need.
