General Hydroponics pH Down LiquidGeneral Hydroponics pH Down Liquid is formulated using food grade Phosphoric acid to create a premium solution for maintaining and lowering a nutrient's pH. Just add a little at a time if your nutrient pH is too high in order to lower the pH to the proper level. Achieve the perfect pH To maximize plant growth, the pH level of your nutrients should be slightly acidic. Experienced growers consider the ideal pH for most crops to fall between 5. 5 and 6.