The majority will starve and with your six line, even a larger cleaner wrasse will be murdered. Sixlines are relentless and depending on tank size, they will not allow any new fish after they’re established. This is a species I’ve found that can’t stand aggression towards it. Usually the aggression is from other wrasses and not other fish outside of the Labrids.
All of them do seem to setup a cleaning ’routine’ however not every fish wants to be cleaned as mentioned above. They are rather effective at reducing parasites as long as the fish the parasites are on will abide. You really want to keep these guys with larger fish and so in a larger tank. This is to help with their diet and smaller fish may get annoyed by the cleaner therefore if it doesn’t feed on frozen already, it may starve. These help with parasites but also help to remove the older slime coat.
Due to their reputation still being extremely bad, yes you’ll be best getting a captive bred AFTER you remove the sixline. Bear in mind that you will have to get rid of your ‘pest’ hunting wrasse and so if you have a sandbed you’ll want to replace the sixline with something like a Halichoeres assuming your tank is minimum of a 3’x2’x2’.
And finally, a photo of the reef will be 10x better than just hearing you as we don’t know what size tank it is (therefore not knowing what sized fish you have which may result in a wild caught specimen starving).
