Protein skimmers or short skimmers are devices that remove proteins together with the smallest particles from the water. Protein molecules are bipolar, i.e. they are differently charged at their ends. Therefore they arrange themselves at interfaces like between sea water and air bubble to a biofilm. When the bubble rises, it expands and more and more molecules can arrange themselves. In the riser of a skimmer the bubbles finally collapse and the remaining protein films lay over each other and become thicker and firmer. During this process many fine particles stick together and are then separated. The efficiency of the skimming process is determined by the total surface of the air bubbles, their charge and residence time. So especially small bubbles have the largest total surface area and rise very slowly, thus increasing their dwell time. If ozone is added to the air stream in small quantities, the bubbles receive additional electrical charge, which accelerates the order process of the molecules. Therefore the foam is much firmer when ozone is involved. Very small air bubbles rise very slowly to the top, which brings the counter current principle of the counter current skimmers to volume limits. The water quality in the aquarium is also determined by the flow rate of the skimmer. This means that the more often the contents of the aquarium are passed over the skimmer per hour, the better the removal of proteins. Different methods produce the bubble mixture: 1. lime wood ejector, 2. venturi nozzles on the pressure side 3. thread wheels 4. needle wheels/dispersersers. Needle wheel skimmers with a simple separation chamber without counter current produce the finest bubbles and a large water flow can pass through the separation chamber. They are currently the Non Plus Ultra.