12-06-2011, 07:50 AM
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You can just replace the cartridge in the filter. In tank that's been running for some time, you have many times more beneficial bacteria in the substrate than in that old dirty cartidge - just toss it and put a fresh one in there. Besides, that filter has the plastic bio-guard gizmo. Also, don't mess around removing the activated charcoal from inside - sure it won't last long, but it can stay in there. As for the surface film, try collecting by dragging a dry paper towel over the surface.