Bact Rox Extra Large is an extremely porous filtration medium designed to be used in all ponds aquariums and aquatic systems for bio-filtration. Each liter of Bact Rox provides over 7,500 square feet of surface area internally for colonization, providing for nitrification and vast amounts of anaerobic or anoxic surface area to foster denitrification. Bact Rox will reduce the levels of toxic ammonia, nitrites and nitrates, as well as phosphates and organic pollutants in all aquaria. It may be used as your primary or only biological filtration medium. It works extremely well in nano aquariums, as well as systems of all sizes. It is particularly well suited to reef systems with live rock including FOWLR systems and will not foster problems that bio balls may. Use in a canister filter, reactor, or other type of aquarium filter with good water flow. Works well submerged or in a drip system. For maximum results, should be used simultaneously with Reef BioPellet Fuel or Reef Micro Fuel, or Flora Viv Prolifera carbon sources and/or with BacterClean M or F, BacterGen M or F, or BacterGen MD cultures, as appropriate, to jump start and maintain the colonization process at elevated levels.