I'm not a big fan of cartridge filters except that they are probably the easiest of all filters to service.
As Romad says, use those filter cartridges until they're falling apart and just rinse them in tank or treated water at every water change so you don't kill off the bacteria.
Now once your tank is established (about 6 months) this becomes less of an issue. Many think that the filter is the only place bacteria will colonize. This notion is perhaps fostered by many filters that use special bio-media. But in an established tank, there is beneficial bacteria in the substrate and some on the decor, so changing a filter cartridge becomes less important. Still, it serves as a good mechanical filter as long as it holds together and does the job and there's no sense in throwing good tools away!
As Romad says, use those filter cartridges until they're falling apart and just rinse them in tank or treated water at every water change so you don't kill off the bacteria.
Now once your tank is established (about 6 months) this becomes less of an issue. Many think that the filter is the only place bacteria will colonize. This notion is perhaps fostered by many filters that use special bio-media. But in an established tank, there is beneficial bacteria in the substrate and some on the decor, so changing a filter cartridge becomes less important. Still, it serves as a good mechanical filter as long as it holds together and does the job and there's no sense in throwing good tools away!
