On this topic, when I set up my 5', I got a bunch of random tetras from Hollywood that a customer had dropped off and they couldn't be bothered sorting. I acclimatised them and dumped them in the tank and with in seconds there were three distinct schools (lemons, xrays, and neons) from about 8 to 20 in number all swimming in different directions doing their own thing. I wish I'd taken a photo now!