In my experience, Banggai Cardinals are like Chromis in the sense that they tend to kill each other off. I first tried a group of 5 Banggai and they killed each other off in my QT and only one made it into my DT. I then tried three more and the same thing happened leaving only one. I then gave up and just hoped that the two that made it would get along and 5 months later they are still alive and doing well. They actually stick together everywhere they go and are never more than a few inches away from each other. I really wish I had more, but I'm done trying and having them kill each other and will just be happy with the pair I got.