I have a 50 gal tank. pretty much over crowded with convict cichlids and a couple barbs. the cichlids have killed a fire mouth, one of their own, and now my rainbow shark. all these fish have been living together for over a year and no problems. now they are all fighting. I have no idea what to do. tank was tested everything checked out. I'm pretty sure I'm feeding them enough. I don't want to loose anymore fish!