I just got my hands on a couple marineland bio-wheel 350 filters. On each side of the intake there are slots for up to four (2 on each side) slide in filter media. I have a couple that came with the filters but I assume the carbon is old/bad. Now I know carbon goes bad and really doesnÃ¢â‚¬â„¢t need to be included in filtration now days unless you are removing medication from the water. Can I just continue to reuse the thin blue/black filter cartridge with the (dead) carbon in it? It doesnÃ¢â‚¬â„¢t have too thick of a filter lining on it. Or would it be preferred and provide a better place for bacteria colonies to grow to use some other insert? Or do the bacteria colonies mainly live on the wheel itself, in which case the filter media would really only be for physical filtration and not biological? I've heard of certain sponges and alternates that work well for bacteria colonies. I'm trying to find a long term solution so I donÃ¢â‚¬â„¢t have to buy 8 new filter cartridges every month.