what is this spongey looking thing next to my shrooms??

[dutchschoon]

Attachment 220097
It has double it's size since about 3 months ago. It looks like sponge type thing with semi transparent tunnel type things in it, however it's not soft.
Any ideas?

 

[petjunkie]

It's a sponge

 

[dutchschoon]

It's very hard though.. I was under the impression sponges where soft?

 

[bang guy]

It's a type of sponge commonly referred to a Colonial Tunicates.