Mystery rock growth

[SF_Ice]

so i recently picked up some live rock second hand that was being held in a drum with some sw, powerhead, and a heater.

After getting 60 lbs home I found 2 rocks with this strange growth. It is slimy and seems to be a living organism. Can’t get any sort of reaction from it.

Has anyone seen this stuff before?

 

[Mjrenz]

Hard to tell, it would probably be easier to identify if the rock was in water

 

[road_runner]

How did it look under the water?
To me it look like aiptasia but closed cause its outside the water..

 

[SF_Ice]

It was in water and I have yet to see it open. I’m hoping tomorrow it will be opened up. If it is aptasia, is it easier to clean off at this stage with a brush or something?

 

[road_runner]

It was in water and I have yet to see it open. I’m hoping tomorrow it will be opened up. If it is aptasia, is it easier to clean off at this stage with a brush or something?

Is it black really?
If black ota not aiptasia

 

[xxkenny90xx]

That's tapioca, my wife gets it in her bubble tea!

 

[DJ H]

It’s sponge

 

[road_runner]

It’s sponge

Black like that?

 

[KrisReef]

It looks like a sponge
or The Blob.

 

[SF_Ice]

I’m hoping to get some action out of it today while it sits in water. Up to this point it hasn’t done anything underwater and looks no different.

 

[Wolf89]

Black sponge

 

[Island Reef 242]

I have seen them on the underside of rocks that I have collected out of the ocean here in the Bahamas. Could not find any scientific description on what they were. I just assumed they might be a type of sponge, but the slimy-ness of them makes me wonder if they are something else. Either way they have never done anything harmful to my tank that I have noticed. They just sit there in dark corners being slimy.