AquaTop s FORZA PFE-9 Power Filter is an easy-to-use dual 3 stage hang on filter that features mechanical chemical & biological filtration. This Power Filter comes equipped with all the necessary filter media to ensure superior filtration. The PFE-9 hang-on back filter utilizes a filtration chamber system with two replaceable filter cartridges enhanced with Aquatop s premium Activated Carbon and dual Bio-cartridges. The Bio-cartridges maximize surface-area for your beneficial bacteria to colonize removing harmful ammonia. The largest model in the FORZA Power Filter Series the PFE-9 also includes an adjustable surface skimmer that helps to promote gas exchange and keep the surface of the water crystal clear and free of oily slicks.