Green sponge?

[jburgi]

So I noticed this growing a couple months ago, but I just thought it was coloration in the rock. I noticed today that it is a lot bigger than it use to be. I think it looks spongy....but it is a bright green color....all of my other sponge is purple or white. What do you guys think? Sponge...or something else?

 

[deton8it]

I wish I could answer this with certainty but I cant. I think it is a sponge. Hopefully someone else can chime in. I too have something like this in my tank but mine is yellow.
John

 

[bigarn]

Yep, it's a sponge.