[Dyllzz31]

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!

 

[Old Newbie]

Convicts are bullies; Firemouths, Rainbow Sharks and less aggressive members of their own species would all be targets for dominant fish. Sometimes fish get along well for a while and one day things change; sounds to me like things changed.

 

[Sinister-Kisses]

You haven't mentioned how many of each fish are in the tank? It doesn't surprise me at all that the convicts would kill off barbs, rainbow sharks, firemouths, and each other. Even a single breeding pair could potentially, and likely would, eventually take over the whole tank and kill off everything else.