Do you have any Euphillia? That looks VERY similar to the flatties that ran through my 25-30+ head colony of Indonesian torch coral and ditched it with just one head remaining. If the tank is Atleast 36” long, get one of the Halichoeres wrasses in there (My personal favourites for flatties are; Radiants - This is pretty 50/50 though, Jades - These can get to 8” eventually and they grow fast, Yellows - Both the silver belly wrasses and the yellow “CoRiS” wrasse are excellent and run through flatties almost instantly). If the tank isn’t quite that big - Pink streaks will most likely deal with it, I never will run a tank without Atleast one of either of those species of wrasse in it.