Is this normal on a bubblegum digitata

[Llg]

I have this feather material growing out of the side of this coral. I pull it off and within a few days it is back and grows rather long. The coral seems fine, but I don't know what this is. Is it just some weird growth point on the coral or something else? It doesn't retract when touched as initially I thought it was a feather duster or apatasia; however, when I let it grow out, it doesn't appear to be that.

Thanks

 

[Highgrade]

Hydroids most likely

 

[Llg]

Hydroids most likely

Should I be concerned? If so, how do I remove them?

 

[Highgrade]

Should I be concerned? If so, how do I remove them?

They can be invasive. You may want to scrub them off then put glue/putty over the area where they reside.

 

[Llg]

So, I tried to cover them with super glue. Sadly, they have spread all over the tank. Would they kill coral?