What ia this tube the Aiptasia is in

[LeafsReefer]

I have this rock with 2 aiptasia and each one is in this tube that appears to be growing. Is that normal? I haven't been able to get either one with Aiptasia-X because they retreat before getting hit with the liquid. Can I just pull them off?

 

[EricR]

Looks more like fan worm / feather duster than aiptasia.

 

[ReefingDreams]

Not aiptasia. Feather duster. Harmless filter feeder.

 

[Katrina71]

Agree with above. Good guys

 

[LeafsReefer]

Oh really? That would explain why I can't kill it. That green ricordia next to it in the first photo hasn't been opening up as must so I thought it was getting stung.