GSP is like a weed, great started coral as you can pretty much put it through nuclear war in your tank and it will still live.
Getting rid of it is the hard part, you can try different injections etc, best way is never to get GSP in the first place
Since Option A was already exhausted as you probably have GSP in your tank and want to remove it, you can do it the old manual way with a few options:
- Remove all loose rock with GSP and boil/dip the GSP grown part, then let it cool and it basically peals off like skin on a chiken (Very brutal process and yes this will most likely kill anything else on the rocks)
- Use a sharp Scalpel/Cutting pliers and anything else you can find to scrape the nice purple film of GSP (usually it's impossible to get the whole thing and you'll notice is growing back from the smallest piece you missed of just could not get)