Marine Pure is the world's best biological filter media, allowing for both nitrification and denitrification in any sort of aquarium (both freshwater and saltwater). This product works by capitalizing on the power of microbes to break down various waste products (ammonia, nitrite and nitrate). Many products share this property to certain extents, but nothing can come close to Marine Pure. This is due to the extreme porosity of Marine Pure, which far bypasses that of bioballs, live rock and other biological filter media, allowing Marine Pure to harbor a much higher number of microbes over the same volume used. Therefore, not only is it the best biological filter media in the world, it is also the most space-saving. A single Marine Pure cube can filter 25-50 litres of water! Marine Pure is also extremely durable and long-lasting. You won't have to even think about swapping them out any time soon!