Sorry for the quick post, was in a hurry last eve.
You can tell it's a Laetacara araguaiae by the way the lateral band curves down onto the gill plate, L. araguaiae is the only species in the genus has that. Also, until they were formally described, they did go by Laetacara sp. 'Buckelkopf.'
While you tank is plenty big enough, keep an eye on your curviceps if you still have him as L. araguaiae are quite a bit more aggressive than their passive cousin.
With your black substrate, he might get more of a purple (like mine did) than blue, but they come from 3 separate river basins so different color forms are quite likely.
