There's no filter floss only foam, but yeah I did consider that initially and may still go down the sock route but I find them a pain to clean and remove, a sponge I can just drop in a bucket, squaeeze and replace, I need to somehow cut the pipes and run 20mm flexible tubing making filter sock removal easy.
Water level is just right, the way I check is to fill tank up till about to flow down the main drain, then simply fill up the sump completely. Voila