What is this?

[Coffee Soundboard]

So I noticed a few things on some frags I wanted to get rid of. They’re currently in a QT tank. Most of the hitchhikers I could ID, except this guys. It seems like some sort of feather duster or possibly some type of hydroid? Those are my best guesses. The arms do react to stimuli and they kind of pull back into their cave thing. Any ideas?

 

[DeniseAndy]

Maybe a baby cucumber? Tentacles look like one.

 

[Coffee Soundboard]

Maybe a baby cucumber? Tentacles look like one.

Would they burrow underneath a coral?

 

[tjohnson3]

Medusa worm… which is really a type of cucumber

 

[Coffee Soundboard]

Thanks! I’m pretty sure it was a Medusa worm.