Protein-skimmers are used in the marine aquarium for filtering the water by extracting the organic waste materials. Modern protein-skimmers chaffs/chops up the air bubbles to fine pearls inside the skimmer pump which rise in the reaction pipe of the skimmer. Foam gets formed on the upper end of the pipe which is collected in the foam cup of the skimmer and thus the water gets separated. One distinguishes between the external skimmers which is used very often in large aquarium and internal skimmers which is mostly used in the technology tanks; there are also cheap Hang-On skimmers which are operaed easily on main tanks if technology tank is not available. Ozone can be added to the skimmer to increase the efficiency of the skimmer.