That looks like apitasia especially if its burgundy in color.
If you don't have anything in your tank that will eat shrimp, put some peppermint shrimp in there and they'll take care of it as we'll as eat new ones as they grow. I've used this method before on my tank, a 125, with about a dozen shrimp. The apitasia literally carpeted all of my live rock. It was gone in about 3 weeks.
If you have shrimp eating fish in your tank, see of you can add a copper band butterfly or two.
My last outbreak of apitasia was the worst I've ever had and I had added a wrasse to the tank (shrimp devourer) since the last time I had cured it with peppermint shrimp.
I was forced to go another route than the shrimp, and bought two copper band butterflies and they cleared the tank in about a month, and it was a really bad swarm of apitasia.
I still have apitasia in my refugium but it never gets up in the tank because of the butterflies.
Get a natural solution man, it's like insurance against future outbreaks and its another species in your tank that you can enjoy.
Hope this helps.