FibberMcGee and fishcounter
I bought three Powder Blue Tangs one time thinking, they school in large numbers in their natural environment, so I'll get a group. They all appeared to be healthy and were eating. Put them into a 125 high, a 60" tank. They were great the first few days, ate voraciously, dashed around the tank mostly together and sparred with each other often. It was exciting to have three in the tank. What a showie fish. Easily one of my favorites.
Then it happened. One day two were buddies and kept the other at bay, wouldn't share food and before I was totally aware of the seriousness of the situation, one died of fright, starvation, harrassment, lonelyness, stress and/or all of the above. I thought, okay, I've still got two and they are getting along fine. Everything was good for a few days when a change in behavior happened, almost overnight. There's always a dominant fish and this time he/she (Don't want to blame a particular gender

) seperated from the other and drove it into hiding and harrassed it so bad I had to tear the tank apart to catch it to give it away. So my rule for PBTs is one at a time like for most Tangs.
They are beautiful!!!