JBL Symec XL is a coarse synthetic filter flosss which does not release any harmful substances into the water. Due to its coarse structure, JBL Symec XL maintains its volume and therefore has a longer filter life than other filter floss materials, which is of particular importance for biological filtering. JBL Symec XL is suitable for use in either freshwater or saltwater aquariums and can be used in combination with any other standard filter material.