I was going to get one more Hifin Platy so my Swordtail would not be as aggressive to the hifin, but all they had were Green Lanterns. I got two of them, and they seem to be staying in the same corner of my 10 gallon tank. One bold one sometimes swims around a bit. The Hifin seems REALLY happy now, because he is staying with the green lanterns. My question is, is that normal behavior? And, I was going to get a larger tank, but they were a bit expensive, so I will get one next week. I was looking at a 20 gallon tank.