Great for Aquaponics and Hydroponics One 250ml (8oz) pH Up and One 250ml (8oz) pH Down Use 15mL (1 tbsp) per Gallon or 3ml per Liter This hydroponic solution does not need to be diluted. The Atlas Scientific pH Up and Down is simple to use and straight to the point. Use this product sparingly. Before you begin adding pH up and down to your water or soil, test the pH to confirm that you need to raise or lower the pH level