Since I refill each of my hydro buckets individually, I follow a regimen of fill my bucket from the bathtub, run it through a rigged filter (brita cartridges), add my nutes (micro first, bloom next, gro if I have it/want it, then additives for cycle,) then adjust the pH. Using the brita filter rig helps reduce the amount of pH down I require, and does a fair job of removing excesses of chlorine and chloramines which can build up in excess when you mix nutrients together (it happens naturally, you just want to control the chlorine content and type.)