We have had some issues with invasive brown clove polyps in one of our display tanks. We read online about some success with treating the tank with Panacur a form of wormer. Our experiences was mixed, here's what happened when we tried it.
Dipping newly purchased coral is something that should be done from the very start of a marine tank. Its makes for good husbandry and helps avoid problems down the line. Unfortunately combinations of excitement, lack of knowledge and inexperience mean many people don't and may never do unless they have a problem.