What is this grey stuff in this rock??

[sensei]

the rock has some blue mushrooms but it also has this grey stuff the inflates and lets water in.
any idea what is it? is it good or bad??
thanks

 

[XNavyDiver]

My guess is it's a type of sponge.

 

[Kamden Uelton]

Chicken Liver Sponge (Chondrilla nucula)

 

[sensei]

is it good or bad to have it in tank??

thanks again

 

[Kamden Uelton]

A mix of both... They provide natural filtration for the tank but they also grow VERY fast.

 

[sensei]

Thanks Kamden,

I also posted some pics of what I thought it was some type of algae in my FOWLR and the answer that I recieved is that it may be a sponge.
can you please take a look at tell me your opinion??
here is the link

https://www.reef2reef.com/threads/what-kind-of-algae-is-this-one.369083/#post-4550855


thanks again

 

[Kamden Uelton]

What you have doesn't look like sponge.

 

[sensei]

Thanks Kamden!

 

[reefwiser]

Could be a sponge or squit nothing harmful actually a good thing. Helps filter your water.