Fantastic thread. So much like the hassles I went through. Feels better to know others have such issues. And it is so frustrating when people say - "Oh just GHA, that's easy". Well, I am still going through it to some extent. Not 100% gone. Great advice from Powerman as well. First: From all the pictures and descriptions, it really seems that you may have BOTH! I think I did. I would get tufts of tough stringy non-fern bryopsis, and then get hair algae growing in and around it. From those pics, looks similar. And that might explain confusion under a microscope. When I scraped with a wire brush, the differences were more obvious. Or maybe it is super-GHA. Don't know. Whatever it is - Nasty. Second: I believe there is no one single cure! If you try X, then Y, then Z, it may not work, ever. But if you do X + Y + Z, at the same time, then you may succeed! For me: 1) Removed the worst rocks. 2) High magnesium. 3) Super low nutrients. (Less feeding, bigger skimmer, Carbon, Purigen, phosban, turf scrubber.) Yes, all of those, all at the same time. 4) Stronger flow. 5) Wait months. It is receding and bleaching. Although the now-white tufts are still tough to pull out. Cleanup crew did nothing. Tangs, red+blue hermits, and any type of snail I could find. Oh, and that rock I removed I wanted to save, so I put it in a covered bucket. About 3 months later, that stuff was still there, and still green. Not growing, but not dead. The only light was through the side of the bucket, from simple house lighting.