The "NEW" form of bio filtration. Sintered quartz material with an extremely craggy surface area for intensive bacteria colonisation for optimum biological decomposition of harmful substances. Colonised material will lower nitrites when in heavy concentrations. It has a netural pH & is suitable for both fresh water & marine aquariums. It is specially shaped to create a current-like water flow with vortex effect and has very low dust due to abrasion resistance and is extremely long lasting.