Could this be a Medusa worm?

[OldRed1]

Apologies for the grainy video. Just barely managed to get it on camera before it retreated into the sand bed.

 

[bushdoc]

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[Blake509]

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[vetteguy53081]

Apologies for the grainy video. Just barely managed to get it on camera before it retreated into the sand bed.

The head looks like that of a sipunculida worm related to peanut worm but their tubes are short and does look indeed like a medusa worm which is actually a leg less sea cucumber but has shape of a work and are reef safe although Not welcomed in my tanks