Based on personal experience: When I had 5 Ruby Barbs, they behaved poorly and fin nipped, when I upped the quantity to 6, life was grand. The Ruby Barbs where very active keeping to them selves and was fun to watch. I would recommend a minimum of 6 Ruby Barbs. When I had 5 Tiger Barbs they kept to themselves in isolation. They didn't bother other tank makes but clearly were in distress. When I upped the quantity to 6 things did not change. When I upped the quantity to 7, they started to be more 'fun to watch' but showed signs of being scared around certain fish. When I upped the quantity to 8 (present stocking level) replace your TV with them, they school really nice and always entertaining. I would recommend no less than 7 Tiger Barbs.