Between and eclipse 1 hood, system 6, and penquin 330... i've been spending a butt load on replacement filters. So i was read about replacing the marineland cartridge with a fluval sponge (203/204) in my Eclipse 1... perfect fit. So i looked at the fluval 104 sponge and compared it to the system six cartridge. Perfect fit also.
Just strap the sponge onto a stripped cartridge and your done. Some bio media can be added in the pockets that hold the carbon.
Won't have to worry about spending any money on the eclipse's untill the sponges get worn out (couple months at least). Just need to rinse them clean during water changes in some tank water.
Nice little trick for all of you using a system six.