An apparatus for monitoring aeration in a fluid of a hydraulic circuit is provided. The apparatus includes at least two measuring units configured to connect at a first location, and a second location of the hydraulic circuit. The measuring units are configured to measure pressure, temperature, and density of the fluid at the respective locations. The apparatus further includes a computing unit configured to output aeration values of the fluid at the first and the second location based on the measured pressure, temperature, and density by the two measuring units. The apparatus further includes a correlation unit configured to correlate aeration levels at the first and second locations based on the measured aeration values.