Hi, I just recently had several fish die in my 155 gallon tank. I had a dog face puffer, Fox face , Coral Beauty and emperor angel. I had the foxface and puffer for two years with no problem than I got a emperor while he was a juvenile and coral beauty and for 8 months there was no problems. Foxface was the first to die than coral beauty than emperor and just today puffer died. I did notice scratches down dogface puffers body. Last night he was starting to turn black in color and today he was completely black and dead. I was told that when emperor gets bigger and older that he would get more aggressive. I tested my water and and all of my test were fine . Water changes are done bi weekly and like I said earlier before I got emperor and coral beauty I didn't have no problems. Im so pissed right now and just want to know why did this happen ?