Sponge, algae or egg sac?

[dave in nj]

These came on some live rock I purchased. It seems to be getting larger. It is a white blob with a smooth shiny surface.


Can anyone ID it for me?
Thanks and happy New Year!

 

[bribo12]

Looks like a sponge

 

[coralbandit]

Looks like a sponge also to me...
If you find a 'valve' on it , then may it might be a Tunicate...

 

[Sniperhank]

It is Cthulu. It will eventually develop tentacles and attempt world domination.

Or it's a sponge.

 

[54seaweed]

Don't think its a sponge as it's shiny looking sponge usually dull looking