bought an apogee 420 fullspectrum usb par meter and have taken readings with the pumps on so i could see what it reads in normal circumstances (kessils350w &360w tuna blues, so with the surface flow they have quite a shimmer and i suppose i would take the average par. could i avoid math by simply turning off flow and take a straight non shimmer reading, or would that be less accurate? i appreciate the help !