I have a very similar setup. It's a 33 gallon. I have 7 tiger barbs and one rubber-lipped pleco in that tank. Tiger barbs need some swim room, so I didn't want to overcrowd them. Add some plants, driftwood etc., and you'll have nice looking setup. I also heard (not sure how accurate this is), that having an odd number of tiger barbs might reduce excessive aggression towards each other.