The diffusor draws in fresh air from the outside of the aquarium and this enriches the aquarium water with oxygen. The supply of oxygen is necessary particulary for sparsely planted tanks cold and sea water aquariums and oxygen rich loving fish. Small and simple to fit. Air flow can be adjusted with a pressure adjusting clamp. For Eheim Installation KIT2 and for hose 12/66mm and 16/22mm for filter 2036 2048 2071/73 2171 2215/17 2226/28 2250.