Experience the power of a zero bypass filter design! When it comes to the latest in filtration technology, it doesn't get any better than Aquatop's Forza Zero Bypass Hang On Power Filter. This compact, powerful, yet quiet hang-on the back filter takes a three-dimensional approach to zero bypass. Aquarium water is pre-filtered before passing through the pump and entering the filter cartridge. Water enters the enclosed filter cartridge filled with activated carbon and can only exit one way, past the Activated Carbon and through the filter cartridge! This ingenious design filters every single drop of water, making the Forza Zero Bypass one of the most efficient aquarium filters on the market. Powerful 3-Dimensional Filter System with Zero Bypass Unique Ultra-slim Design Filters Every Drop of Water So Your Tank Stays Crystal Clear, Suitable for Fresh & Saltwater Aquariums up to 20 Gallons