Hydroid?

[MaMe]

Are these hydroids? They go back into their tube when disturbed.
If so, how do I get rid of them?

 

[DancingShark]

Looks like them from goggle search.

 

[LPStandard]

They look exactly like the colonial hydroids that were on my old rock. I was never able to easily remove them.

 

[Vincent100]

Yep hydroid