Although pretty, GSP is like a weed in most tanks. I keep a small patch on an isolated rock in the sandbed and prevent it from getting to the main rock formations b/c its a pain to remove. Like mentioned above, fragging can be done with scissors or pieces can be torn by hand.
If it's on the rock and you want to kill it, you can use a kalk paste like you would with aptasia. Its resilient so multiple treatments are likely necessary.