I have a bluegill that seems to hang out with my dovi constantly and protects the dovi from other fish in the tank to an extreme. The bluegill will violently attack the Butti & Nile Tilapia when they bother the dovi. WTF?
Thats actually a green sun i believe not a blue-gill. But nice! You would be surprised how aggressive bluegills and most fish in that family are. They can really hold their ground.
Two Green Sunfish in two days, actually it could be a Warmouth too it's hard to tell from the pic, both are Lepomis but I'll go with GSF I don't see the red eye of the WM. These fish can be extreamly aggressive and look kind of like a mini LMB. It's capable of doing some damage.