Monday or Tuesday our parrot fish developed a bump on his head. He has had some major changes in the past couple weeks. Switched from a 50gal w/ other parrots to a 30gal w/ no other parrots only a couple silver fish (have no clue what they are but they are fast growers, we had larger versions in the 50gal before we switched tanks. They were recommended by the store where we purchased the parrot). "Pappy" has always been inquisitive and would come to the surface to feed. Since the developement of the bump his (I say him but I have no clue if its a male or female) actions have gone from inquisitive to more aggressive in nature..if you look a him through the tank he will quiver and rush the tank. We aren't quite sure what's going on. Is this bump a normal thing?