'reef safe' is a relative term...
this is from the Blue Zoo site:
Of the so-called reef safe triggerfishes, species from the genera Xanthichthys and Melichthys are the clear choices with the former thought by many to be even more reef safe than the latter. They generally stay small (under a foot), and they have relatively peaceful dispositions. Members of the genus Xanthichthys, like the Blue Jaw Triggerfish (X. auromarginatus) are considered the most mild-mannered triggerfish species available in the hobby, and they happen to be beautiful to boot. Growing to only a foot in length, this peaceful triggerfish is rivaled only by the triggers from the genus Melichthys for consideration in a community reef tank. Like all species from the genus Xanthichthys, the Blue Jaw Triggerfish feeds primarily on zooplankton in the water column, and so it requires plenty of swimming space. The upside of their diet is that they tend to not go after sessile invertebrates as often as other triggers do, but the downside is they may go after other zooplanktivores such as chromis or cardinals. The Blue Jaw Triggerfish is sexually dichromic and is often offered in pairs in the hobby.
As was stated above, in addition to triggerfish from the genus Xanthichthys, species of the genus Melichthys can also do well in a reef tank. The Hawaiian Black Triggerfish (Melichthys niger) is another good, albeit larger (up to 20 inches), choice for the community aquarium. Like the Blue Jaw Triggerfish, the Hawaiian Black Triggerfish feeds from the water column and, consequently, does well in similar habitat. The Hawaiian Black Triggerfish is reported to be more likely to eat ornamental crustaceans and small peaceful fish than the Blue Jaw Triggerfish. The Pink-Tail Triggerfish (Melichthys vidua) is the only other triggerfish commonly available in the hobby that should be considered reef safe. In fact, it is many hobbyists favorite reef-safe trigger given that it is smaller (to 16 inches) and generally readily available (read cheaper). Again, like the Blue Jaw Triggerfish and the Hawaiian Black Triggerfish, this fish is a zooplanktivore that feeds in the water column and is more likely to ignore invertebrates and corals (although this fish is known to eat ornamental sponges).
