Conspecific Tolerant Fish?

Just wondering if anyone can give me an idea of some fish that will not end up killing others of their kind. I'm considering doing a species tank where I would have 5-6 of the same fish, rather than an assortment like most reef tanks.

I thought cardinals might be good for this, but would love to hear a few other ideas.

 

I had a trio of Bangaii Cardinals, and one picked off the other two over a two month span. I know I'm in the minority here though, as Cardinals don't normally behave this way. Black Axil Chromis (Chromis atripectoralis) don't pick each other off often either. A lot of Anthias do well in large groups, but are finicky, and more difficult to keep.

 

Thanks- I was thinking pajama cardinals actually. They tend to be less aggressive than even the Bangaii's. Also, should have mentioned that I have a 40g breeder, so anthias are out

 

What about a group of 5 firefish? I know they can be territorial to their own kind, but would having 5 help spread out any aggression?