Jdaddyks, the pH range for hydroponics should be between 5.5 and 6.5 after adding all nutriments and supplements, and it should be allowed to vary within that range as different nutriments are taken up by the plants at different pH levels. I adjust the pH of the water to 6.0 using pH down and check with pH test strips (I have had bad problems with the test pens and do not trust them). At the mid week top off, I check the pH of the reservoir and add water , pH ed to 6.0, to top off. I do not adjust the pH as long as it is in the range of 5.5 to 6.5. The pH will change as the nutriments are removed from the water. I use this change as an indicator of how the plants are taking up the nutriments (as just a S.W.A.G). Several grows back, I nearly killed off some of my plants by chasing and adjusting the pH to stay at 6.0, that's one of the benefits of hydroponics, if one gets into trouble, just drain the reservoir and start over.