ID (May Be a Tough one)

[don1234]

Growing on the back side of my star polyps....been there about two weeks. Looks like some type of cocoon or sack. It is kind of soft, but durable. Its the black substance if you can call it that. Looks as though it may have poures.
Any clues.

 

[don1234]

After briefly researching maybe black sponge. I did find a picture of something called black bermuda sponge? I also found a picture of something that look similar but was green in color and it was sponge.

 

[culp]

it could be a sponge but to tell you the truth the pictures were not clear enough for me to be able to tell.

 

[keri]

I vote sponge as well - don't take it out of the water though, that's bad for them (If you want to keep it)

 

[ophiura]

It is a sponge IMO, but you will not probably get beyond that in terms of an ID unless you know exactly where your rock is from. "Sponge" is usually enough.