Help IDing please?

[ashlynnmurlo]

I was looking in my tank today and saw this thing that looked like a circle feather on top of a stick sticking out of my live rock. While looking at it it when inside itself and into the Rock, and hid out in there for a minute or two. Then it would come back out, and go back in everytime I would look at it. I got a picture of it though, is this a feather duster? I have recently noticed other things in my tank that look similar to this except they are on the bottom side of rock and completely white with no brown color to it like this one.

 

[sam.basye]

Yep, a little feather duster.

 

[ashlynnmurlo]

I'm pretty sure that's not a bad thing to have in your tank, so awesome! I haven't added anything to my tank in about five months, could I have just not noticed that I had feather dusters this whole time? Or where do they come from?

 

[Betta132]

Feather duster. He's harmless. And it's entirely possible that you've had them the whole time and he's just now grown big enough to be seen, or it could be that's a new one and the originals are on the backs of some rocks. Dusters that live inside rockwork, like that one, are pretty much never seen when the rock is out of the water- they retreat and stay retreated.
The ones under the rocks are probably also feather dusters, unless they look like pineapples. If they look like mini white pineapples, they're pineapple sponges.