Its actually a Bolivian Ram, 30g would be preferable, but one or two would be ok in a 20g. No, they do not need to school, they actually like to pair, 1male to 2females. Correct me if you need to. I would say 2 in a 20g max, but 3 can do well in a 30g... you can breed them too, they are hardier than German Blues - and bigger.