I have 2 Brichardis in a 56 column with a few more tangs, 2 daffodils, 2 julies and cylindricus. The latter stay near and in the rocks. Do Brichardi pursue other fish in rocks if there is plenty of open swimming space?
If they are a breeding pair....then watch out! Otherwise, they are pretty peaceful but if they establish a territory in the tank, then the individual brichardi or colony will vehemently defend said territory. They absolutely have no fear, attacking tank mates more than twice their size.