I have this same algae. A few people on a Facebook aquarium both id'd it as red turf algae. I have looked into red turf algae treatment and the only consistent way to treat it is with peroxide. If it is isolated on one rock I would remove that rock and either isolate it in a tub and treat it in the tub to try and prevent it spreading. Mine is to the point it is all over my rocks and powerheads are all covered in it. I have read that some Mexican turbo snails will eat it, but it is not a definite yes or no with them. That is about as far as I have made it with my outbreak, I will be more than happy to try and update you guys on how it goes when I begin treatment.
I am going to try a couple turbos hoping I can get lucky. My last resort solution Im planning on is to move all corals and my nems to a 12g frag tank Im building and leave the fish and everything that doesn't need light to survive and just shut the lights off for a week at a time and see what it looks like after each week. I'm going to bookmark this thread but if I don't respond feel free to shoot me a pm