This is located at the base of my pink pulsing xenia, it has been "stinging" it almost nightly and the xenia will wilt and have an indentation where it touched it. It lives in a clear narrow tube about .25'' on the base of the rock where the xenia is attached and retracts if I try to touch it. Any ideas what this is? Is it a problem?

the worm/thing is at the base in a small clear tube

this is a little after it touched it

Vermetid snail.

They can't really sting anything, but it's possible their slime/mucus (used to catch food) can irritate the coral.

Yup, no stinging going on there, chances are that the xenia will just either overgrow it or grow around it as time goes on.

thanks for the info guys, it has been bothering my xenia so i went ahead and put a spot of super glue over the tube, hopefully that will do it