You could try a drop in filter like the Klir Di-4 possibly. Got one on my Waterbox 70.2 and whilst it's a bit of a pain to clean or change a roll. I'd much rather do that once every few months or so than pull out socks every few days to a week.Is there a reason to keep the filter sock in with the reefmat? I am working on setting up my 900 and want to find a roller mat that works well. In the filter sock chamber would be awesome, but I don’t know that it’s big enough area for it to make sense.