What is this green thing?

[maevepotter]

Sorry for the terrible picture, but it's bright neon green on a little stem. It's coming out of the live rock I bought.

 

[sfin52]

could be many of things mushroom or a sponge would be my guess bit the pic is very blurry and can't make out detail.

 

[KJ]

Google Neomeris.

 

[sfin52]

that's a real good possibility

 

[maevepotter]

I think that's definitely it; thank you so much for the ID.