If you have that many, no chemical control will be effective, I tried every chemical method there is and they just kept on coming back, were I killed one 5 more poped up.
The final solution for me was two fold:
Pepper mints in the refugium and frag tank and a large copperband in the main tank.
IMO biological control is the only permanent solution, you have a choice between peppermints, copperband and berghia nudis.
Berghias are relatively delicate and copperbands are a difficult fish to feed and may bother clams and other stuff but peppermints are IMO the way to go unless you have a fish that will eat them.