Oceanlife Carbon Active is a pellet of activated coal selected for aquarium water filtration. It absorbs toxic yellow medicinal chlorine substances and produces bad odors from the water making the water crystal clear and pure. We recommend the use of activated charcoal on a stable basis following the instructions at the side. It can be used in any type of filter (fluid bed forced passage filtering stock etc.). The best performance is with a forced passage that allows the water to flush the product across the surface.