This is a Reverse Flow Calcium Reactor which will siphon the water from your sump and pump it up through your media for better flow and less fouling. Its 10 inch x 10 inch footprint and 20 inch height, along with its 4 ½" crystal cast acrylic chamber will easily slip under most aquarium stands. The top flange has a full gasket for a tight leakproof seal. The unit is assembled of all non-corrosive materials and top quality valves. It's powered by a smooth running Mag-Drive 250 which will eliminate the need for a full time secondary pump. PUMP NOT INCLUDED. RECOMENDED PUMP IS THE MAG DRIVE MODEL 2. Rated up to 400 gallons.