Zoas with something else?

[Jmanning]

I have a rock about 5"x10" covered in zoas that I have had over two years and tonight when I got home I looked into the tank and saw some sort of green slime looking stuff wrapping around some of the stalks. It doesn't appear to be hurting them.
I was wondering if anyone could tell me what this could be. some sort of sponge or something? It doesn't look like any algae I've ever seen
thanks

 

[cujo6984]

its probably a sponge i have some zoa's with some purple sponge around them

 

[afboundguy]

Can you take a pic? Sounds like a sponge but hard to tell without a pic...

 

[jbishop]

My guess is sponge or algae. I have a yellow sponge around some of mine.