so if the sock catches everything from very fine particles on up, then the filter is essentially not receiving any particles from the skimmer except those that are so fine they pass through the sock and pass through the sand filter. I believe these work I am just not understanding how they help the filter. it seems like they take the place of the filter. initally I thought they filtered in addition to the sand filter. not either, or. I am really not trying to be difficult, I am trying to understand. (sometimes I am not the sharpest knife in the drawer.)