If you don't want to take down all of your rockwork...
You can use a DIY
fishtrap using an inverted 2 litre bottle, which works wonders (be patient with this), or if that doesn't work, you can grab a couple of friends and some nets and see if you can't get them that way... I prefer the bottle method to nets though..
Or you can take down your rockwork if there isn't a lot of coral or anything that will perish, and catch them that way. The fish don't know where to hide anymore, and it'll be a lot easier to catch them. Good luck!