Yikes, that is some population! If you have that many showing, there are probably a ton more. Do you have any wrasses in your tank? Coris, mystery or a sixline?
I would use FWE to beat up the population and try to get a wrasse in there to manage. Read up on them, they can release a toxin so be ready to do a good water change 45 min after you dose. When I did it, I double the recommended dose. But please read up, there have been some unlucky reefers out there in regards to FWE so know what you're getting into.
GL