About a week ago, I added a 5" Australian copperband to a social acclimation box in the system. I was concerned primarily about aggression from the group of tangs. The copperband started eating frozen quite well day 1 so I considered myself lucky. There was no attention from the tangs while in the box and so after a couple days decided to release the butterfly.
Immediately after the release the gem tang started to take swipes. The gem is also about 5". I also have a 6" chevron tang who started taking cues from the gem and also started becoming aggressive. I was fortunate and the copperband willingly swam back into the acclimation box unharmed.
A couple days later, I decided to try again. This time, I deployed a mirror on one end of the tank, and placed a clip with Nori. I also fed the tank heavily. The aggression from the gem was less sustained this time, but any time he would see the copperband he would take a swipe. The chevron and other tangs all were more mellow. The copperband was doing a good job evading the gem and I decided to give it a little more time to see if things would settle. I turned out the lights early and the aggression stopped. In the morning, I fed the tank heavily first thing, added fresh nori, and kept the mirror going. Unfortunately, all this was ineffective and the gem continued to be aggressive. The butterfly was unharmed, but wouldn't survive if this continued. Again, he willingly swam back into the acclimation box.
While he was in the tank, I witnessed him slurp his first aptasia! So, the Australian copperband who was eating frozen and had eaten some small aptasia was a keeper.
I was careful when sequencing the stocking of the tank, but there are always tradeoffs. I wanted in herbivores early. I wanted clams and wanted them added prior to a butterfly. And that's I arrived in the current predicament. So the final tactic was to attempt to reestablish the pecking order by catching the gem, purple, scopas, and chevron and allow the copperband to get settled into the system.
I caught all the tangs yesterday, and the copperband has been released in the display. In a week or two, I'll attempt to release the tangs back. If the aggression resumes, they will be rehomed and I'll start with smaller tangs as my last resort.