I need to know what this is

[mrmashashi]

I posted a picture of this a while ago and everyone said I should wait a week or so until it fully opens. This is all the open it got and maybe someone can ID it for me. Personaly I think it's a sponge.
http://home.comcast.net/~silentarrow/Picture_006.jpg

 

[ophiura]

It is a tunicate, also called as sea squirt. It is a filter feeder, with water pulled in through one siphon and pumped out through the other. It tends to respond to movements, which a sponge will not do.

 

[mrmashashi]

oh cool! filtering is good.

 

[ophiura]

They often don't do well in home tanks, especially those that are not supplemented with "liquid" foods or preparations for filter feeders.