I have 6 green tiger barbs that are very peaceful... they are with black neon tetras, a gold gourami, a malabar puffer and peppered cory cats. My ratio of tiger barbs are 1 male with 5 females. Everybody gets along. No nipping, and the only chasing they do is with each other.
I think it depends on each fish temperament. I have species that normally should not get along but they do, they are well fed and plenty of plants to play in.