What is this thing?!

[ColorCopies]

Can anyone tell me what this white thing to the right on my mushroom is? It's kinda squishy and it looks like it has a mouth like a coral would have. Thank you in advance.

 

[powdertang05]

looks like a sponge to me.

 

[DSC reef]

Sponge, harmless filter feeder

 

[GoPitt88]

Yep, a sponge

 

[saltyfilmfolks]

Nice piece too. I've had those same feather dusters in the same spots in my tanks for quite literally a couple years.