I have had this fish for a couple of years and I actually got him from Petco but they had no idea what he was. I am wanting to add more fish to the tank but since I do not know what he is thats a bit of a problem...
What size tank is he in? He looks pretty stunted and i believe he might be a warmouth. How many spines does he have in his anal fin? (The one on the bottom in front of his tail)
He is too stunted to be ID properly. It could be either a green or a warmouth. If it was in feeder fish shipments, the chances that you have a green sunfish.