Why don’t you just use an aquarium rated filter pad, like they sell at your LFS, Petsmart (or online if you must)?
They shouldn’t contain any added chemicals, just PET/polyester (polyethylene terephthalate). Use scissors and cut to shape.
Lifegard Prefilters and Felt pads work really well in sumps and overflows. By placing a pad in between sump baffles or any place that water is channeled through the pad, it will allow the pad to collect floating detritus and other particles in the water column. BRS suggests cleaning or replacing...
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