Is one chromis better than two?

[Torvik9]

I'm thinking of adding a blue-green chromis to my tank - they're peaceful, affordable, and I think they're really pretty. I've got a false perc clown, six line wrasse, and watchman goby already, and I'm wondering how many chromis I can safely add. My inverts are a few CC, a CC star that's leaving soon, and a pin cushion urchin. No skimmer on this tank, just doing weekly water changes. I'm using 40+ lbs of live rock and a hang on filter with chemi-pure and carbon pads - how many chromis can I add before I hit my max bioload? Am I already there?

[rileyon]

Keeping chromis in small groups isn't ideal. They tend to be more aggressive in pairs or singles, the stronger one often bullying the weaker. To minimize aggression, it's best to keep them in a larger school, this way the aggression is distributed more evenly among the group.