Red Sea berlin air-lift is a high performance, low cost internal skimmer based on the berlin triple-pass principle. The air-lift is powered by a lime wood air-stone attached to an external air pump, these compact units are easy to install and maintain. The triple-pass is combined with a powerful venturi air injector, greatly enhancing the efficiency of the skimmer. Air bubbles and protein rich water are concentrated in the narrow inner tube, ensuring good mixing and maximum surface contact. The air/water mixture swirls up the inner tube into the wider reaction chamber, causing a relaxation of the turbulent water and separation of the protein rich foam at the water surface, which rises into the collection cup. The air bubbles move down the chamber by the force of the water current until reaching the air return skirt located at its base. The skirt effectively enlarges the diameter of the chamber, eliminating the downward force on the air bubbles. The bubbles then rise up through the chamber against the downward flow of the water (counter current), causing great turbulence and increased contact time. The venturi air injector produces a consistent quantity of fine air bubbles, ensuring a large surface area for collection of waste materials. Rated for 350-liter/90-gallon aquariums. Measures 17-inch height by 4-inch diameter.