I just got an RO/DI system and don't know how I did without it for all that time. Either way you always want to adjust your PH AFTER you add nutes. I learned the hard way by adding a single drop of PH down to 5 gallons of watter and watched my PH constantly plummet to 2.0. Adding nutrients will help to buffer your PH. I know that Advanced Nutrients has buffers built in and Barricade is made to just such a thing. Plain 0ppm waters PH will dance all over the meter without anything to hold it.