Any fish that isn't too slow moving or skittish, and doesn't have long fins. Platys, swordtails, most tetras, corys, danios. Avoid angelfish, gouramis, guppies, and the like.
You'll have better luck with any fish if you add some more tiger barbs, at least two more for a group or 6. The more of them there are, the more they nip each other and the less they nip everybody else. You could add a couple regular or green tiger barbs, so you'd be getting some variety and boosting your tiger barb school