Michael, thanks for the reply. I think this is something different than you had/have. It is very difficult to manually remove and it spreads pretty rapidly.
My tank originally had an outbreak of Dictyota and manual removal, GFO, carbon, and water changes wouldn't touch. The Dictyota was beginning to take over the entire tank. In an act of desperation, I used AlgaeFix Marine which wiped it out.
But, then Bryopsis, GHA and this stuff started taking over. Again, conventional treatments did nothing to control them. I ended up dosing Fluconazole and it wiped out almost all of the Bryopsis and GHA in less than a week. As of Monday, it looks like the Fluconazole is having an effect of this pest as well.