Sera CO2 test carbone dioxide for the permanent testing of the CO2 value in the aquarium water. The optimal CO2 content is very important for a good plant growth and the right living parameters of your fish. The package content is sufficient for approx. 90 fillings and can be refillied. Sera CO2 permanent test+ permanently monitors the CO2 level in aquariums according to scientific standards+ allows precise adjustment of the CO2 level, for splendid plant growth+ elegant glass container for inconspicuous installation+ complete kit with glass checker, syringe, and evaluation chart for precise water analysis+ with a readily understandable video tutorial for easy use+ sufficient for approx. 90 fillings