DYMAX CO2 Indicator SolutionThe DYMAX Crystal CO2 Indicator Solution is every aquarium or planted tanks essential tool. Keep the CO2 levels in your tank consistent by checking it regularly. This kit contains a 10ml CO2 indicator solution. Guide: Make sure your test kit is clean. Drop 5 drops of CO2 indicator into the glass checker and make sure it is stored in the bulbous side of the valve with the opening facing down. Attach this to the side of your tank, completely submerged