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I found a new product called SuperCartridge. It is a replacement cartridge for Marineland and Tetra filters that has more surface area for bacterial growth and a removable foam insert that is impregnated with carbon for chemical filtering. I have used them on my Penguin BIO-Wheel 170 and 330 filters for about 3 months now. The even better news is that the replacement foam inserts are much cheaper than buying Marineland's Rite-Size cartridges. You can read more about them here.