Eheim filter media are made from high quality materials and are free from harmful substances the media kit is a complete filter media kit from eheim professionel 3e and contains a fine filter pad a coarse filter pad 4 litres of mechpro 2 litres of biomech and 2 litres of substratpro for mechanical and biological cleaning of fresh and saltwater aquariums the coarse filter pads through pre filtration remove large particles from the flowing water increasing the length of time between cleanin