Tank is way too small for all the species involved. The fish you mentioned which you didn't know the species of is a jag or wolf of sorts if you ask me, and these guys get monstrous and enjoy mutilating anything they can get their jaws on, and they can get their jaws on anything. If you're looking for a fish nastier than your dempsey, you already have it. in a 120L tank, you should be limited 1-2 cichlids that grow to be 5-6 inches, not 5 cichlids that grow to be a foot long, regardless on if you plan to upgrade.
Don't just get a bigger meaner fish that you can't accommodate to kill or bully your dempsey, cause then it's gonna kill or bully all your other fish too. It probably isn't even too nasty of a fish, any cichlids can get nasty if there isn't enough territory to claim.
Don't just get a bigger meaner fish that you can't accommodate to kill or bully your dempsey, cause then it's gonna kill or bully all your other fish too. It probably isn't even too nasty of a fish, any cichlids can get nasty if there isn't enough territory to claim.