35% Sulfuric acid is CropKing's recommended material for commercial growers to lower the pH of nutrient solution. We use sulfuric acid because it is cost effective, readily available and can be used without adjusting other nutrients in the fertilizer program. The amount of acid needed to properly adjust the pH depends on your water source. Please contact the CropKing team with questions on how to determine the correct amount of sulfuric acid you will need to add to your concentrate tank.