Help with ID please

[Countryfanjmm]

We've had this mushroom in our saltwater tank for some time now and it was doing really well. It was about 1.5-2 times the size it is now. I'm wondering if this thing that is growing next to it is to blame for it declining a bit. It retracts completely into the "neck"??? (for lack of better words) sometimes. When it is fully out, the head of it is about the size of a nickel or so. Thanks in advance for any help anyone might be able to offer.

 

[chenzo9999]

It is a tube worm (feather duster). Just a filter feeder and harmless

 

[College fishman]

That's a feather duster. Harmless, 95% sure it doesn't have any stinging abilities

 

[Countryfanjmm]

Thanks guys. I was hoping it was harmless.

 

[MacDracor]

Everything above is correct. It's a feather duster and has no stinging ability. However, depending on proximity and sensitivity of the coral in question, it's constant touching may be annoying, causing the retraction. My guess though is that if its a real problem, the mushroom will either get over it, or move.