Looks like a Blueberry

[Creben]

what is it!? i can see small holes in the top, and other than that it just looks like a blueberry..

 

[rdahlke1105]

Do sponges come in blue? Looks kinda like a sponge.

 

[Bifferwine]

I think it's a blue sponge too.

 

[Creben]

great! they just feed off of light too? i dont want to kill the poor guy

 

[rdahlke1105]

Sponges are filter feeders. Do some research on sponge care and you should be good to go.