Would you have suggested adding a African cichlid to this tank? OK. So not all employees at a pet store give bad advice. But this one did.I disagree on the pet store bit. I work in a pet store and im there to make sure the fish gets a good home and the customer is satisfied
"big ball of light, spits out dinosaurs" - Mac, Primeval New World
With tiger barbs, the females are bigger. I just don't think you have a lot of room in a 30 gallon for much if you want to keep the tiger barbs. Your tank is not big enough for a tin foil barb, or a common pleco. If you re-home those two fish, you could get 16 more tiger barbs. Having a large school of them should help to spread out the aggression among a larger group. You could then add a rainbow shark, and a bristle nose pleco. That would make a decent tank IMO.