white coral or algea?

[coops22]

i have some white silky, somewhat inflated pillowy looking stuff growing on one of my rocks. its only about the size of a quarter and oval in shape.
any idea what it could be? and is it safe?

 

[coops22]

it seems to be getting bigger and looks like a kind of alien pod with veins.

 

[kmk2307]

Can you post a picture? How thick is the "tissue?" Does it break apart easily? Is it growing on live rock? Where is the rock from?

 

[coops22]

its on live rock yes, from a specialized tropical fish shop, not sure of origin. i dont think it breaks apart easy, havent touched it. one of my hermit crabs walked on it and it just kinda squished indented where its leg was on it. i cant give you a picture i dont have a scanner or a digital camera unfortuneately, sorry.

it resembles a pillow in many ways, but it does have visable veins/branch like things in it. and its bright white.

 

[coops22]

its about a 4th of an inch thick i would say. or thinner.

 

[moggyhill]

like a sponge?