Many things come into play here.. Some we don't even know or understand completely.
Warm water will only hold "X" amount of DO, doesn't matter how good of Pondmeister you are. 70 deg water may not even do it, so 80-85 is going to be impossible.
I just re-read Bill's post and I agree with the 65 range being the max temp for good health of a fish that requires tremendous amounts/levels of DO.
