Monterey Bi-Carb Old Fashion Fungicide, 4-Ounce Potassium bicarbonate soluble powder for control of powdery mildew on roses, vegetables, grapes, fruit trees and ornamentals A more acidic nutrient solution will neutralise bicarbonates on its own This in turn reduces the amount of acid needed to control the pH in the reservoir and thus reduces the possibility of acute phosphate accumulation