I've generally heard that 6lines, particularly as they get older, don't ever really play nice with other wrasses. I'm sorry to sound pessimistic, but I don't know if remixing rocks to enforce a new territorial boundary will really work (it might work for the tang, however). The problem with wrasses is that they cohabit the same niche (i.e. compete for the same foods) and a pecking order seems to be important to them.
If it was me, the ace I'd keep up my sleeve is to plan to keep them in separate tanks if need be. And besides, you can't honestly expect us to believe you have one tank, right? Or at least if you do, you can't possibly be satisfied with one tank, right? And if you are, then ... um ... please tell me your secret
