Sorry for the bad pictures. It’s i. My fluval 13.5 and I didn’t scrape off the back side of it. You can kind of see it but they look like white webs all over the chamber in the back. Looks as if they’re keeping the chamber clean of detritus in the first one but the second chamber is a little dirty and they’re starting to grow in there. Should I let them stay and clean up my chambers or will it become a problem?