This thread has everything you need to know about using fenbendazole. My first post is #472 with a few follow ups as well. There's a lot of detailed information from others who have used it successfully too.
If fenbendazole, doesn't work. Then you will need to break down aquarium and srart over. That is where I am at today with main display. Good luck as allot of people had success.
If it's just on certain rocks. My advice would be to immediately remove them and discard. If it's everywhere then fenbendazole is your best bet
I quite unintentionally eliminated mine when I added a pencil urchin to the tank to eat GHA... The Algae stayed, the cloves got eaten... The urchin found itself rehomed to the LFS lol