Plant like object - corals not opening

[qlcing]

Not sure if this is the right place.. but can anyone identify the attached plant formation thing?

I have noticed my corals are refusing to open lately - my parameters are fine but these things have gotten HUGE.

Thank you!

 

[aKlevans]

Looks like feather dusters to me.

 

[JALIASC]

Looks like feather dusters to me.

Agreed, they aren't harmful

 

[Oohkris123]

They are a indicator of a healthy system