Help! There's something on my coral

[elepe]

There's a black and white spot growing on the side of my coral. It goes in and out of the white tube. Can someone tell me what this is? I attached the picture below. Thanks !

 

[CafeReef]

Feather duster. Completely harmless. You can break if off if you want. But It wont hurt your coral.

 

[Sapelo]

+1 feather dusters
Great cleanup crew member, filter feeder, nice score