Clown triggers are unique little creatures. They swim around your tank examining the contents, both living and decorative, then take a bite of whatever fancies them. They then return to take another bite, just to make sure that they really didn't like it the first time. Sadly, they seem to like most everything they bite....
If you want a trigger for your reef, and are prepared to deal with the bio-load, consider a Sargassum, Crosshatch or Blue Throat. There are a few others, but they get quite large.
-Rob