I have a glass tetra, which was giving me problems ,and chasing my angel fish around in circles until the angel had to hide behind plants for a moment of peace. I asked what to do, and was told that tetras like to be in groups. So I went out and bought 2 more, now two of the tetras chase the third around. I don't know if this is normal behavior, or if they are attacking. I don't want any stress in the tank, i'm tryin to avoid ick, which killed two of my sharks about a month ago.