Eheim Night CO2 stop

The magnetic valve allows you to cut off the CO2 supply to the aquarium if necessary, for example, to regulate pH or during the night. Cutting off the CO2 supply at night can save up to 50% of CO2, as photosynthesis only occurs during the day when plants absorb carbon dioxide and release oxygen. At night or without light, plants consume oxygen, so CO2 fertilization would not be beneficial.