There isn't a truly reef-safe method that will always work unfortunately. Methods that are known to kill marine ich (hyposalinity and copper) will kill your reef. Your choices basically come down to let them live with it and hope it doesn't kill off your livestock (many fish can live with it for a long time but they are often suffering even if they seem otherwise healthy) or remove the fish, treat them and leave the display empty for 8 weeks. Tough choices. Cleaner wrasses and shrimps will not cure it and neither will raising the temp, garlic and other saltwater myths. The only true cures are hypo and copper and leaving the display without fish for 8 weeks. Good luck with it! Keep us posted.