Gluttons. Mine ate a ~1.5" triangular rock one night when it fell from the cross beam over the tank... Must have broken it up or something because he was fine afterwards, bur he didn't look comfortable while it was poking out his sides... I loved having him, though.
Odd how the fish you got as a hitchhiker ate one you paid for and they have nearly the same value... If you like the firefish better, you could offer it as a trade to the LFS. Technically, you'd be giving them two for one.
Nice hitchhiker, I just can't see me spending more on it's meals than my own.