Weird ball thing in my tank

In my nano tank I have this weird ball shaped thing. At first it was in my chaeto then it got bigger and moved to the rocks. It then climbed up the rocks (slowly) using those long filaments. It also has those filaments going into the water column.
I thought it may be some kind of sponge but I didn't think those moved.

I have a slightly better picture at home so will add when I get there if needed. It's white with what appears to be a green mass inside it.

 

Some sort of urchin?

 

Nope not an urchin...it's attached to the rock...and has been in the tank for 8 months...perhaps more.

 

maybe a sponge or sea squirt

 

I believe its a sea squirt.

Found this pic online:

 

I think this is now the 3rd thread I've seen here with something similar to that, the first thread it was ID'd as a sponge (and we all learned that some do move LOL). Maybe check some of the other threads in the ID This! section, they shouldn't be too far down the list.

 

I think that's a tunicate. If its been in the tank for 8 months and nothing's happened to this point I wouldn't be too worried.

 

It has been bugging all day. I used to have an image of a sponge very similar to what may be pictured in your image, but can not find it. I was very surprised to find out that some sponges can move pretty good, I would have never guessed. Anyway here is a link if you want to look at it.



SpongeIDFAQs

 

Thanks Corailline...I totally forgot about that site and I found the name ....according to them it's a "(white) syconoid sponge. Sign of a healthy, stable system" yay....found a much better picture of them too.

I wasn't worried just was mondering what it was...I have pinapple spnges and smoe sort of purple encrusting trunicates in the tank as well....came in on the LR.