How many blue chromis should I get?

[pirate]

I got 3 blue/green reef chromis and they almost always seem to be schooling. They are toghter then apart and then back toghter. I've had them for about 2 months now and they were schooling like this in the other persons tank as well. But I do have a couple of damsels that like to chase. I was thinking I might add a few more into the mix, but too many other fish that I might want!