Like hair algae, it can drive one to this.
I have to go along with the others on the sandbed. It seems almost impossible to get rid of. In the tanks we corrected in, removing the dsb solved the problem.
However, I see you have wrasses like I do. My new tank will incorporate some sandbed, albeit shallow in most places. Like some others I have talked with, we figure to replace a portion of it every now & then.
Also a way to control phosphates is important. For me, its my scrubber, but also many are having good success with Phosban or the more expensive one from Germany.