Use Rate: Mix Hydra-Phix into the spray tank before adding other components such as fertilizers or pesticides. Add enough to correct the pH based upon the color of the solution. As a general guideline, 4-8 ounces of Hydra-pHix per 100 gallons of water will decrease the pH from 8.5 to 5.0. This may vary due to the particular characteristics of the water source.