Help With Mushroom Asap!!!!!

[nmhs2]

I have a mushroom green colored not sure which exact one. I noticed a block colored thing that looked like a polyp growing out. And the wierd thing is when a fish goes near it or say i go near it towards the glass the polyp almost hides and retracts to nothing, then it will come back out when theres no movement. WHAT IS IT, A PARASITE!!?? I have no idea I just want my corals to be safe

 

[nmhs2]

SORRY I MEAN BLACK NOT BLOCK

 

[dc_909]

Pics?

 

[madamo]

Sounds like a feather duster.

 

[Lotus99]

Sounds like a feather duster to me, too. I have a couple that are black.

 

[awcasper]

too weird... i also have a green disco mushroom w/ a feather duster under it.

i thought it was an anemone at first.