Fine and coarse activated carbon filter pads for adsorptive filtration For adsorptive filtration - also for removal of harmful chemical substances (chlorine, remains of medical treatments etc.) - there are special activated carbon fine and coarse filter pads as a filter insert. Adsorptive filtration is usually only necessary in the start-up phase of the aquariums or after use of medication. The filter media should only be used for a short time (ca. 4 weeks) and then removed or replaced.