AquaClear power filter represents one of the most versatile hang-on filter systems available. The five models available provide a complete selection of flow rates for the most popular sizes of aquariums. The filter s unique design allows for up to six times more media volume and the longest water to media contact time in the industry. The AquaClear flow control will reduce the flow by up to 50% without harming the filters motor or impeller. The AquaClear filter media system includes the patented innovative re-circulation grid and multi-filter media stacking. The re-circulation grid allows water to be passed through filter media more than once when slower flow rate adjustments are selected allowing superior contact time and significantly contributing to water quality.