It looks like a sunfish to me
Some kind of sunfish. Definitely put it back, you're not only risking the lives of any other fish in the tank, but of the sunfish itself
That is definitely a green sunfish, they can be very aggressive and with a bigger mouth than most sunfish species it will eat just about anything. Keep an eye on him.
Yeah this thing had little teeth
Do you have anything else with it in that tank?
Yeah a jack Dempsey and an African cichlid and a pleco
Hahaha my blue gills did that. I had to get rid of them but they had personalities those were the only fish I had that my parents liked.