I have a 150 gallons saltwater tank with fish and live rocks. In the tank, I have 1 large unicorn tang, 1 hippo tang (large), 1 butterfly fish (large), 1 foxface (large), 2 clown fish, and 6 small yellowtail damselfish. These fishes have been in the tank years. They getting along with each other every well. Yesterday I decided to purchase a large Yellow Tang for the tank. I went through the acclamation procedure and placed the fish in the tank. it seems to be peaceful for few hours and all sudden the hippo tank and butterfly started getting aggressive and swing really fast and bullying the yellow tang. I observed for 30 minutes and still seen the chasing. I decide to turn off the light and seeing every one getting calm down. the yellow found his spot and staying there. This morning I turned on the light in the tank, just few minutes later, I saw the yellow tang fin split and tail torn off.
Thanks so much!