PH Down Growth Technology pH DOWN contains orthophosphoric acid (H3PO4). The concentration is 81%, which is very strong so handle with care. Some other products on the market are considerably weaker, so check the concentration before buying. This is a very dense liquid and should feel much heavier than water. What pH Down Does The concentrated phosphoric acid pH Down can be added to almost all liquids to lower the pH. It is important to maintain a pH range when growing plants using hydroponics and aeroponics. Each plant has its own requirements, but most require a pH of between 5.5 and 6.5. To maintain this pH level, pH Down can be added to the nutrient solution sparingly. How to use pH down PH Up and Down can react explosively to each other if they come in contact. Even small amounts of pH Up or pH Down could explode. Both pH Up and pH Down are corrosive, and can cause skin irritation and even burns. Use with caution and keep out of reach of children.High Quality pH adjustment in a bottle. Features CRC cap for safety. Highly concentrated so only a little is needed. Always dilute prior to use.