These critters are called "Bluestripe Pipefish." They have set up a 'cleaning station' in a puka(hole for you Mainlanders) in the inner reef not to far from Sandman's Patch. They have been there for the last 6 months functioning not unlike the drive thru car wash at the local Shell Station (no pun intended). Every morning I see a queue of assorted fish patiently waiting their turn to be cleaned of parasites. They run the gambit from Surgeonfish to Moray Eels. I'm guessing that the tactile interaction with the Pipefish, not unlike the head massage my barber used to give me back in the day, is also "value added," and keeps them coming back for more!