I have 2, and have had to put them into a separated tank. Would you like to see the results of letting them go free together in a half-gallon? I wouldnt recommend, especially if one is more aggresive then the other. You need AT LEAST 4 or more females, so that dominance is set easily amoungst them all. I have both girls in a separated tank, and then still flare at each other. One girl got some of her scales ripped off, and torn fins and tail, while the other got complete damage of her tail. They nipped at each other while I wasn't there!