Mine never bothered any of my corals. But one thing I would say is be careful what type of fish you have, as these can make a tasty and expensive snack for quite a few marine fish.
As for the worm, under stress they will leave their tube, but you can put them back in by gently easing the bottom into the end of the tube. Obviously wear gloves and do it in the tank. Then place on the sand and the worm will reverse back into its tube onits own. They also do shed their crowns when stressed or moved, all of mine did it when I had to move them back after a white spot outbreak but they all grew them back within 2 weeks just smaller. And they can also grow another tube. Just make sure they are out of predators way while they do it.
When out of their tubes they can look dead so you have to be carefull not throw away a live worm
![Frown :( :(](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
They are also pretty tough too so I would always give them a second chance .