Anyone know what this is?

[Mighty]

It looks like a spider coccoon attached to my live rock. Any ideas? This is the best pic I can get.

 

[HoCkEyGmC]

tough to tell but my guess is some type of sponge.

 

[Fluff]

Definately a sponge.

 

[Fierro Nights]

i had some sponges in my tank, if it looks like it has a small feather duster on the tip then it may be a pineapple sponge, i have a bunch in my tank.

dont bother trying to find information on them though, using the words " pineapple " and " sponge " will only bring up sponge bob square pants in almost all search results.

sponges are good though, help clean out the water.

 

[melosu58]

A simple filter feeding sponge.