I made some Xenia angry once (nearly full strength peroxide dip) it snotted my whole system like crazy. I siphoned what I could into a filter sock in my sump with carbon in it. That seemed to work.
This seems to be slightly different. It is slimy and attached to my rocks and back wall
It is tan in color. I can't find anything on this but it does not appear to be algae but has a fuzzy slimy quality. Weird