This is a Aquarium pH Up Liquid for Fish Tanks - 120ml (Aquatopia). This product is used for raising the pH of aquarium water from acidic to neutral or neutral to alkaline. Most fish can adapt to subtle changes in pH but extreme changes should be avoided as big variations in pH can be harmful to fish. All pH changes should be made gradually (over several days) to allow fish to adjust to the change. Aquatopia recommends using a dosage of approximately 1ml for every 10 litres of water. A measuring cup is found on the product lid. Allow 30 minutes before testing again. Remember you want to make pH changes over a long period of time (days not hours). The recommended change in pH is 0.5pH points daily.