What is this???

Have no idea what this is. My best guess is some form of sea sponge? It was on the back of one of my frag rocks that I just went to move. Sorry about the pics, I was a little rushed.



TIA guys & gals

Edit: I know of the feather duster's

 

could it be a feather dusters and a sponge ?

 

I was thinking sponge too. I should note that I know what the pineapple dusters are, and that I wasn't in question about them.
If it is a sponge, is it something that is safe in there?

 

The white cylinders are tubeworms. Beneficial filter feeders. Part of why live rock is "live".

 

OK I typed my response as you were typing yours. Nevermind.

But yes the other things (I can't think of the name now) are perfectly fine. Again, they're part of why live rock is "live".

 

Sponges are fine. It is a good thing. They like flow. I have a few myself.

 

i think its fine to leave it alone. sponges are rather picky about conditions so it prolly wont grow very far, i had one that got 5 inches tall reaching up to my seio power head then when i moved the power head it shrank back down to a blob

 

Thanks! It wasn't noticeable there about about a month ago, and now its about 3-4 inches long. Guess that's a good sign of the tank doing well.