Today I found that 4 of my 5 Emperor Tetras had mysteriously died over night. One is still alive and doing well. They seemed to fight with each other often and I curious if anyone else had similar issues? Could the one dominate male have killed the other 4? In all my years of fish keeping I have never kept these fish, so I am unaware if they are more aggressive than they are advertised as being? Everyone else in the tank is doing well, no signs of health problems. I had two baby Apisto in the tank, and I believe one may have been killed by them, as they chased the other fish relentlessly, but now that the 4 are gone I see the one Apisto coming out more.