I have the same stuff in my tank, came in on a coral I was holding for a buddy. Its very persistent stuff, i got the nutrients to a point its not spreading anymore, but just could not get it to die. So after some research, I decided to use hydrogen Peroxide. Took out one rock as a test, used a 50/50 mix of peroxide and DI, sprayed the rock very well with the mix, left it out to sit on the plastic for 2 or 4 mins after spraying. After I let it sit for a bit I had two rinse buckets with saltwater I double rinsed it then put it back in the tank. I have to say that this is working and the stuff is dying. Pain to remove the rocks and coral but worth it to me to get rid of the stuff. Anyone want to chime in and tell me this was a bad idea because?? I do have about 400#'s of LR in remote sumps that have none of this, its just the display that has around 60#'s or so.
( sorry for short sentances an or misspelling's on the Iphone difficult to type. )