a year ago i was told by friends and local forums to not add a six line if i plan to have my tank wrasse dominant tank. but i did add one, so with a pair of flame, a pair of rhomboid, a mystery, a velvet, a pair of lineatus.
i was flamed for adding a six line and a mystery wrasse on the same tank for i was told that they will harass and kill each other. but they did get along fine even after a year later they swim together and eat together and even stare at the tank for hours to see if there is an aggression, none, zero, they get along fine.
altho the difference might be i have a 90g with a lot of hiding places which i think makes them less aggressive for they have their own territories.
just my 2 cents.