A short term cartridge for the eheim pickup 45 to aid the removal of harmful chemicalsr these carbon cartridges are for adsorptive filtration and will aid the removal of harmful chemical substances chlorine residues of medications etcr ideally used during the start up stage of the aquariums or after the aquarium has had treatment with medicationsr the filter cartridges should in any case only be used for a limited period ca 4 weeks and then replaced with a standard cartridge