All triggers in the genus Xanthicthys are reef safe, which includes the bluethroat, redtail/sargassum, linespot, and crosshatch triggers (and a couple others that are rare in the trade). Niger triggers (Odonus niger) are similarly safe, however they will sometimes eat small fish in the wild and will probably do the same in a reef (just avoid darts). Pinktail triggers (Melicthys vidua) are safe with coral, however they will attack some inverts and may nip at fins. I've recently been forced to reset my reef, and I am considering trying a small pinktail or redtail trigger this go round.