ID please? Worm thingie

[bkwonnn]

Hi guys,

I have these weird things in my rocks. I thought they were part of coral, because it has some sort of sweeper tenticals.
When I come close you see the white part retract.
Any idea what this is?

 

[bkwonnn]

Another pic

 

[EeyoreIsMySpiritAnimal]

It might help if you circled or otherwise indicated what exactly you're asking about.

 

[bkwonnn]

You are right.
Here I try again.

 

[bkwonnn]

With Zoas retracted

 

[ISpeakForTheSeas]

With Zoas retracted

That's a large vermetid snail species:

I've never heard of rapid spreading with the larger species, but they seem to be much rarer than the smaller ones, and people tend to remove them as soon as they see them - so they might just not be in the tanks long enough to spread like the smaller ones.

 

[EeyoreIsMySpiritAnimal]

+1 on vermetid.

 

[bkwonnn]

Thank you all