Urgent something stinging my xenia!

I have some live rock in my tank. In one gorgeous piece there are xenias (they were already on the rock when I purchased it). They are not pulsing, so maybe they are anthelias? Not sure. Anyway, a few nights ago I noticed that the xenia was missing a piece of it and not looking good. Last night I noticed another piece. My son noticed a very small white tube (with purple towards the bottom of the tube) and a very small, almost clear tentacle (?) coming out of the tube. While watching, the tentacle touched my xenia and stung it! This xenia was sitting on a little rock, so I picked it up. My son said when I did this something came out of the tube. I didn't see anything. Can anyone identify this?

 

Hi,

You may want to check out the links and see if it is a vermitid worm/snail or a spionid worm. Both links are excellent resources.

Snails That Worm Their Way Into Tanks by Ronald L. Shimek, Ph.D. - Reefkeeping.com


The Worms Crawl In… by Ronald L. Shimek, Ph.D. - Reefkeeping.com

If you can move the xenia I would do that or you can attempt to use super glue or expoxy to seal the hole if it is one of the worms mentioned above.