Carborundum stone with fine bubbles that increase oxygen levels, low CO2 emissions and raises pH Air stone disc increases dissolved oxygen level in water, give their fish a comfortable environment Air stone disk can be used for a long time, if the oxygen is reduced, it is clean and can easily be washed for reuse Just connect aquarium air pump, applicable to 4mm diameter pipe Ideal stone disk for freshwater stone, saltwater aquariums , hydroponic water, or aqua farms, aquatic crops, create amazing beautiful underwater scenes