I'm doubtful emeralds will help much but no harm in trying.
I am doing an experiment. I have 3 small patches. Luckily they are very slow growing. I made a flat thin "pancake" out of standard reef epoxy putty. I formed it to the rocks with my fingers. It won't actually stick but forms a cap and will stay in place as long as direct flow isn't too strong. I have a vertical surface to treat where it will blow away, but plan to secure it with stout plastic toothpicks drilled into the rock.
The idea is to deprive it of light. I did this about 3 weeks ago. I lifted the caps occasionally and didn't see any change. But recently I confirmed it is indeed thinning & receding. So it may just work. But it will probably take some time but I'm in no hurry. It might help to supplement this tactic with a good scrubbing and/or peroxide application if one is so inclined.
I plan on keeping the hard epoxy caps around after treatment in case I need them again. But eventually I plan on having some encrusting corals there which should out-compete it, hopefully.
Good good luck to you. .