Just started new tank and I don't know what I did wrong. I have a 55g tank that I cycled with 2 yellow labs for 7 weeks. Ammonia and nitrite levels are at zero and ph is 8.2. I thought I was ready so I added fish to my tank last week (17 mbuna). One by one they started to die. I saw signs of fin and torso damage which led me to believe that some were fighting even thought I bought lesser agressive fish. They all stayed to the outside perimeter of the tank. In less than 1 week all of the other cichlids are dead and the original 2 are still alive. Am I correct in thinking that the yellow labs caused all this damage? They were a lot smaller than those that I added. Could the fish that I added have a disease? If so I would expect my original fish to have contracted it by now. I am at a loss. I want more fish, but I definitely don't want the same thing to happen. Should I take the original 2 out and see how it goes before adding others? Any advise you could give would be greatly appreciated. Thank you!