Is this an anemone or a sponge?

[matman4u]

I have this white piece growing on a new piece of live rock.
Any ideas what it could be. There is some white fleshy slime on the same rock on the other side.

 

[madtek580]

I have something very similar in my tank, I've always thought it was a sponge

 

[acrodave]

Sponge

 

[eran]

sponge

 

[matman4u]

What kind of sponge? Is the white slime part of it? Is it ok to leave in my tank?

 

[acrodave]

what kind who knows..is it safe to leave in yes

 

[kaskiles]

Is that a pineapple sponge?

 

[matman4u]

I have had a pineapple sponge before and it does not look the same.

 

[clowns101]

sponge