Ready-to-connect CO2 fertilization system for the optimal supply of all aquarium plants in freshwater aquariums from 40 to 300 liters, helping to prevent algae growth. Easy setup: screw the pressure reducer onto the bottle, connect the hose with bubble counter/check valve and diffuser. Adjust the bubble count - done. Reusable CO2 storage bottle. The hose is securely attached with hose fittings, and 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.