Eheim filter media are made from high quality materials & are free from harmful substances. The Media Kit is a complete filter media kit from Eheim professionel 3e & contains a fine filter pad, a coarse filter pad, 4 litres of MECHpro, 2 litres of bio MECH & 2 litres of SUBSTRATpro for mechanical & biological cleaning of fresh- & saltwater aquariums. The coarse filter pads through pre-filtration remove large particles from the flowing water, increasing the length of time between cleanings. Then Eheim MECHpro pre-cleans the flowing dirty water & purifies it. Eheim bio MECH, acting as a bio-mechanical filter medium, traps large & fine dirt particles with its dirt-trapping pockets. At the same time, Eheim SUBSTRATpro provides the cleaning bacteria with the best conditions for new colonisation. Thus harmful substances are broken down naturally. & before the water leaves your aquarium, the fine filter pad traps the finest dirt particles. Eheim Filter Media Kit for professionel 3e 450, 700 & 600T at a glance: Fine & coarse filter pads Trap large & small dirt particles in the porous material Good colonisation conditions for bacteria cultures Reusable several times over: rinse & squeeze out while cleaning the filter Eheim MECHpro Spiral-shaped mechanical pre-filter material for trapping large dirt particles Reusable: very easy to clean Eheim SUBSTRATpro Bio filter medium made from pearl-shaped sintered glass for very dense colonisation of bacteria Better reduction of nitrite loads & longer intervals between cleaning Eheim bio MECH Mechanical-biological water treatment made from p H neutral material without water hardeners Reusable: just wash out carefully, in order not to destroy the bacteria cultures