Update: I took him back to the Pet store. I decided to buy him yesterday and then do research on Black Belts (since I didn't know much about them) when I got home. Unfortunately, he gets a little too big for the tanks I have right now.
The thing that throws me off though, is that he doesn't look like the pictures provided above. He was REALLY dark with 3 or 4 vertical black stripes going halfway up his back half - almost like a juvie Severum.
If he does end up being something different than a black belt (and smaller) I might have to go back and get him...