That is a ringtail tang. I had one for a little while, but it unfortunately did not live long. They can get pretty big. Over a foot long. Hope he has room to grow.
Should be for a while. If you saw the adult coloration on those, they are stunning. I was pretty disappointed when mine died. It was actually mislabeled at a LFS, and I had to figure out what it was once I got it home.
I hope you have better success than I did and it becomes a beauty.