White thing growing on rock ?

[davedaster]

Hi I have a white thing with a hole in the middle growing on my rock any ideas pls ?

 

[AMaintC]

How old is your tank? Or how long has the live rock been in there? I think I have the same thing. It started to the left of the large hole looking similar to yours. The inside of the hole filled with the same thing and the little one to the left started shrinking...? I've looked all over sponges but yours is the closest I've seen to what I have.

 

[davedaster]

The rock has been in my tank for about 2 years I found this link https://www.dfwmas.org/Forums/viewtopic.php?f=2&t=64649

 

[Starchar]

had the same thing in my tank previously, sponge.