Cutting Edge Solutions pH DownCES pH Down Concentrated pH adjustment liquid, acidic buffer lowers water and nutrient solution pH. Highly concentrated, use conservatively. Slowly add to pure water or nutrient solution, at small intervals. Note beginning reading and then test pH. Repeat small application process and stir well, until desired pH is achieved. Amount of CES pH Down required for adjustment will vary, depending on the strength of nutrient mixture and purity of the water