What IS this!?

[Mmmarishaa]

Found this in the tank this past weekend and have no idea what it is. In the center of the picture there is a hornets nest looking thing. Anyone have any clue what this could be?

 

[ErinCahir]

Looks like a sponge to me. Harmless filter feeder.

 

[mariobrothersleeve]

+1 erin

 

[Mmmarishaa]

Thanks, I bet it is a sponge.