I have three tanks with fish in. One large tank with cichlids and a smaller on with just on Malawi who does not want to integrate, and finally I have another smaller tank with small fish in it.
So, on Tuesday I bought a lovely orange cichlid that was going to be a tank mate for the Malawi, but he did nothing but chase her constantly. As I wanted her to thrive I put her in the communal big tank. She seemed okay at first, but then a few of the other fish chased her, but it settled down, well, for a bit until the Parrot fish and her BFF a yellow Lab decided to go after her. Now, she was not tiny, and only a little bit smaller than most of the tank. There are fish in there that are the same size as she was, so that should not be a problem, and I have not had problems introducing others to the tanks in the past. But, this was not to be, as I discovered on Wednesday evening. The Parrot slammed her on the side which caused instant swim bladder problems. I moved quick and put here in an isolation pod in the tank, but knew she would not make it as I have seen this in the past. Thursday early hours she died, and was buried in the garden with the other animals from our 20 years here. It was a shame as she was very pretty. I have decided that I will not be getting any more for the two cichlid tanks unless the fish are large and I know they can handle themselves.