I have had a gorilla crab and I found out because he destroyed acros! This looks like what I have been battling for the past month! Three of my acros are loosing pe and color is fading away, I couldn't figure it out. Until yesterday I hit them with some flow and collected anything that came off so I can examine closer. I'll post pics of what I collected in a min. Moral of the story, they were attached to the acros and I couldn't even see them!