Help with this one please

[Malemew]

Hi

I purchased a few extra bit of live rock a few weeks ago as I hear you can never have enough.

When I got the rock there was what I can only explain as the skeleton in the shape of a deep saucer or upside down mushroom head.

Since then blue stuff has started to fill the skeleton on one side and a bit of dark pink on the other. It's as if the skeletons skin is growing back

Would anyone know what this is?

Many thanks

 

[carried]

Looks like a sponge to me.

 

[Saratj1]

Either sponge or maybe a mushroom