CO2 fertilization system (without bottle) for the optimal supply of all aquarium plants in freshwater aquariums from 40 to 300 liters and for the prevention of algae. Easy setup: screw the pressure reducer onto the bottle (not included), connect the hose with bubble counter/check valve and diffuser. Adjust the bubble count - done. Ideal for aquarists who already own a CO2 bottle. The hose will not slip due to hose fittings. The check valve prevents water from entering the bottle. The correct CO2 concentration in the aquarium water is monitored using the included CO2/pH permanent test and can be adjusted if necessary.