Richard, sorry about the situation, several recent posts about fish kills you should read.680 CC per acre in your situation may be too many too soon. Running your aeration probably lowerd you DO not increased it. Your oxygen bank in an unaerated pond in warm water is primarily in the top few inches so pumping too much lower water to the surface only dilutes the O2 level. This is one of the reasons for starting slow. The standard startup procedure is 15 minutes to start and double it everyay and on day 8 and you are running 24/7 PROVIDED you observe nothing negative in that time frame.You need to know your pump and diffuser capacity to calculate how your aerator is sized, it may be too large or too small for your goal.
