Schooling fish need schools to prevent stress, and stress can cause a fish to die. However, there are other reasons to keep your tiger barb in a school, even if he survives on his own. When a schooling fish is forced to be alone, he picks up the "fight or flight" tendency. Sometimes they'll hide so much you'll never see him. Usually they pick fight, though. They become super aggressive, and will take on decent sized fish until there is little left of the other fish's fins. The larger the school of barbs, the less aggressive they are.
They need 5-6 + per group or they will die from stress ...
It will get lonely> stress> ; more stress> death
