Hi. I have 7 bleeding heart tetras. The largest is terrified of its own shadow and stays in the darkest corner of the aquarium. I have to feed her completely separate from everyone else in the tank. She never schools with the others. Why? The other 6 are always up front in the tank, ready to eat. They out eat my other fish and are pigs. The past few days I have noticed that 2 of my tetras swim at each other at 45 degree angles and will circle like boxers. What are they doing?