The Nitratreductor 1000 is an anaerobic biological reactor for removing nitrates from marine and freshwater aquaria. It has a large volume of 4.5 gals and an internal circulation pump. The Nitratereductor 1000 works with a flow rate of .25 to 1 gph. In the absence of oxygen this situation promotes bacteria that metabolize nitrate. Denimar powder or Deniballs are used as an organic energy source. To monitor this process, it is possible to use a redox potential controller (ORP controller) in conjunction with an electrode inserted in the inbuilt PG13.5 port. The Nitratereductor 1000 is a closed unit that can be integrated into filter systems, but may also be installed to stand alone under the aquarium. Dimensions excluding electrode (l x w x h): 7" x 7" x 22". For aquariums up to 250 gallons.