Just picked up this drop in manual fleece roller for my IM 40L AIO. Really happy with the placement next to the protein skimmer but I have a question. What do I put in the open space at the base of the plastic towards the cone end (pictured). It looks like a place for additional filter media such as polishing pads or filter floss but I'm really unsure of what the point of the fleece would be then. Also, anyone with experience with a manual roller, how often should I be rolling it? TIA