This guy came in as a Striated Bristletooth (Ctenochaetus striatus) but I'm having my doubts. I haven't been able to find many good photos of C. striatus, especially juveniles, but I don't see any with a white lyre shaped tail.
Sorry for the less than stellar photos, but s/he won't stay still.
Sorry for the less than stellar photos, but s/he won't stay still.