The supply of oxygen is of great importance for all moderately planted aquariums, both cold and marine aquariums or when keeping fish that require special oxygen. Air must also be introduced where a light hood or cover covers the aquarium surface. The oxygen present in this environment would be consumed very quickly. The Eheim diffuser brings fresh air into the aquarium water from the outside, so that the water is gradually supplied with oxygen. The small device is mounted at the end of the outflow hose and attached to the aquarium wall, possibly creating a horizontal injection angle. This simultaneously creates good water movement. The air hose of the diffuser is installed in a place outside the aquarium. Dosing can be done as required using the supplied regulating valve. The device mixes the supplied air quantity with the inflow water, which is sprayed under the water surface by the pressure of the filter pump.