I agree with MITJ 100% about "pretty much" foolproof and InHum has a valid point as well. My suggestion would be a combination of the two, know your pH and ppm before hand. While pH pefect will do it's best to balance pH it is a chemical technology that is meant for the "mass", so.. if your water is not part of what most folks use (over 6, under 9PH and <100PPM from the tap) don't bother with pH perfect because you're better off using the unused PPM to pH your water to it's correct value. Feed at 1/4 strength recommended. I've been using it for two weeks now in 7.2 8PPM water and it works wonders. Never pH, no issues - when a deficiency pops up (Cal/Mag did - I was running no CM because I didn't realize my tap ppm was so low) it's fixed instantly so I know the pH is correct for nutrient absorption. Good stuff.