<a href=showthread.php?s=&postid=7792039#post7792039 target=_blank>Originally posted</a> by theop
They are very hard to get rid of. Some people have had luck peeling off the purple mat rather than scraping it off. Putting marine epoxy over them can work sometimes. You can try to kill them like you would aptasia with kalk paste.
If you can take the rock out, you can break off the piece that has the GSP on it.
I've decided to keep my GSP on a rock on the sand bed not touching any other rocks. This way you can trim off the mat as it grows onto the sand. This prevents it from getting on other rocks where you dont want it and it makes for a good way to frag it.