Key Features Filter cartridges need to be replaced because cartridge floss will become blocked with trapped material and the carbon capacity for removing toxins will become exhausted. The Algaway sphere’s ability to remove algae food will be exhausted. Replace your cartridge filter once a month to keep your aquarium healthy, clean and algae free. Simply remove and discard the old filter cartridge and replace with a new cartridge. After cleaning your filter, it is advisable to add Interpet Quick Safe Start to boost the beneficial bacteria population of your aquarium. Services packs for Interpet Internal Cartridge Filters are available in one and three month packs. This three month service pack is suitable for an Interpet CF Mini.