can someone help with an id please

[No Luck]

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The first pic is the damage done the second is what has caused it.
It happens only at night and only every couple of weeks. It leaves a sand like tube behind that is empty when removed. It has completly killed a duncan and now has attacked this millie and a couple of acros. Tx for any help with an id and a way to remove this

 

[terryagi]

The sand tube is only on the coral? It never extends to the rocks at all?

 

[No Luck]

yes it comes out of the rock work. I remove it as far as i can reach. It is usually in one general area.

 

[No Luck]

Any ideas at all?