Weird Yellow Growth on Rocks

I'm not sure if they're sponges or what not... but they are on the top side of the rocks directly under the lights. Before I start stocking... I'd like to figure out what they are. I do have it "live" already. So ID help please.

 

Looks lke yellow sponge to me.

 

I have no clue what that is?

Perhaps a macro image will help.

 

Unfortunately, I sold my macro lens. I might be able to get a closer shot, though. I can't find an image of it any where online.

 

Would love some more input.

 

looks like an odd sort of sponge

 

I have something very similar growing in my tank but it's neon green and growing under a rock in a kinda like cave. But it look exactly the same just a different color.

 

So likely ok to start moving some stuff in?

 

I should note that it only appears to be in lighted areas.

 

Some better pictures...
Yes I pulled the rock out. It looks like there are pods crawling all over it. (I seeded the tank from the Biocube)