Bio-Activ Live Aragonite Reef Substrate is covered with naturally occurring biofilm found in the ocean. The bacteria on the sand are preserved in their natural live state using a patented process with a QX-23 saltwater enrichment solution. Aragonite reduces harmful nitrate, maintains proper pH, enhances buffering capacity and provides essential inorganic elements such as strontium, cobalt, zinc and molybdenum. Instantly starts the cycling process and stabilize inside your saltwater aquarium. Perfect for most applications except undergravel filters. Aragonite Reef Substrate features grain size ranging from 1 to 2.5 mm.