White threads hanging off of a rock?

[Fishwife]

I noticed these white string like things hanging off of my rock with the Gonoipora on it. They don't seem to move, but are getting longer. When I got this picture, I noticed feather like things on the ends. Are these safe filter feeders?

Thanks, Debbie

 

[Brad Miller]

My guess...feather duster outbreak ?

 

[will25u]

Little feather dusters. I had the same question recently. They’re all over all of my rocks.