My last post does need some clarification, I don't want to steer anyone wrong.
My rez holds my nutes that are balanced and PH'ed to feed my roots/plants. Before i add water to my existing rez with nutes and roots/plants, I always PH it. That way I can see what my rez p PHs at prior to adding water, and adjust the PH of the new water I'm adding accordingly. If my PH is high before adding water, I lower the PH of the water to balance the system out. If it's low, then I add water with a higher PH.
I started doing that because I learned (have read) that PH in a rez with roots/plants should not be adjusted more than 1 point per 4 hours in order to not harm roots/plants. I had been adding the new water to rez and then adjusting PH. I imagine that doing so could have been harming the plants because if the PH changes with the addition of new water, an adjustment would sometimes have to be made to correct it. That means that the PH would most likely have to have started at one reading, changed after adding new water to a different reading, and then changed once again when I correct it. Now I add the water with the correct PH to balance. If PH is 5.8 in Rez, I add 5.8 water. If it is 5.7, I add water with a PH higher than 5.7... NOTE: I don't usually raise PH if it reads 5.7 in my rez because most likely, it's going to rise on it's own. If it reads 6.0 I will add water with less that 5.8 PH
I could be mistaken, but it seems that would be easier on the plants.
Again, i hope this helps and clarifies
