Aqua One Premium Nood is a uniquely shaped sintered glass biological media, that is ideal to use in all types of filters. Highly porous it provides the ideal environment for beneficial bacteria to colonise and thrive. Premium Nood acts both mechanically removing solid particles and biologically to convert ammonia to nitrite. This is important in all aquariums as ammonia and nitrite can prove lethal to your livestock. Premium Nood should be used as a permanent filter media and is suitable for both fresh and saltwater aquariums.