Find out what they are, do some research, and rehome them if they get too large or aggressive by popular opinion, you're not going to know if they're aggressive or not based on a 2.5 inch fish!
I've got a little male 2 inch convict in my tank with khuli loaches, black skirt tetras, and a firemouth, and he's behaving himself now, but I know for a fact that as he matures, he's gonna want to rip the other fish bit by bit.
(note, he's only in that tank to grow a bit before I introduce him to my female who is significantly larger.)