This jewel when he was in my bigger tank didn't take stuff from anyone none of the bigger cichlids ever messed with him, when he had a girl friend the two of them took on a 9.5" oscar that ventured to close to their home. Sadly my female died. I am really not sure what to do I have This jewel and a firemouth that is to small to be in the tank with my 9"+ cichlids, I wanted to keep this jewel a firemouth, and another jewel that is a baby 1" right now in QT in my 55g. But if this jewel is going to kill everyone that goes in the tank I can't house him with them, and I can't leave him in the big tank an hope for the best because my daughter gave him to me for fathers day. He might have to live in a 20G (24x16x12), I have not had any problems with him in with my larger cichclids but I have a newish Oscar who has been living with this jewel for about 7 months with no problems but this oscar is getting more and more aggressive as he gets old. I also have a baby jaguar that will go in the bigger tank once he is big enough. I have no idea what the temperament of the Jag will be, but i understand they can be mean.