To prevent the aquarium from leaking, the air hose conveying air into the aquarium from the air pump needs to have a check valve. This non-return valve prevents water from running into the pump and possibly also into the room.
If you’d like to buy the adjustable precision air shut-off valve or are looking for additional information, take a look at our product page: JBL ProSilent Safe
If you need additional aeration; or want to know when you need an air pumps; or why air pumps are needed at night; for all these questions find out more in the Themeworld Aquarium: Air pumps