EHEIM Diffuser p. Diam. 12 16, Diam. 16 22mm for 2036, 2048, 2071 7 The diffuser replenishes the oxygen present in the aquarium and enriches the aquarium water with oxygen. The oxygen supply is recommended for aquariums with a small population or those with a large fish population. Also for cold water and salt water aquariums or for the maintenance...