Deep bed biological filter packed with Granovit media. It is fed by means of a flow diverter, 3178.710 (not included), a slow trickle of aprox 3 gallons per hour, as a result a complete nitrogen removal can be accomplished in an established bed as the deeper zones are anoxic and allow the bacteria which would convert nitrate to nitrogen gas to live. It is ideal for use with Reefpack 505, Riverpack 605 or Comline Filters 3166.500 or 3167.500. Additionally, a mangrove or in the case of freshawater tanks, various emerse plants, may be grown from the filter providing both a decorative look and further waste removal.