As for science, 8ppm dissolved O2 is the most you can get using air, and 10ppm is about the most you'll ever see recommended. BUT I think the most important thing is consistency, finding a procedure that gives you good results and then being able to repeat it. You can get cheap, in-line flow meters for your O2 or air line, and consult charts to determine ideal flow rate and time. But you can get equally good results from something like "X twists of the valve, Y Mississippis" (works fine for me.)