Gouramis in large numbers don't always work out either...keep in mind the gourami's you buy at stores are males...the females lack color and don't sell, so most fish stores don't carry them, most can't even special order them. The males tend to be a bit nippy with eachother, in my experience.
Some tiger barbs can be nippy, and the smaller the school the more nippy they are. it seems in a school of 20+ they are so busy nipping and bickering with eachother they generally leave the other tankmates alone.
I had a small school of 8 tiger barbs in a 29 gallon...they even nipped at my corys...small school and small tank is a bad idea from my experience.