ID?

[DYIguy]

I pulled all the rock out of the 13g to remove/ treat for bubble algae and found this on one when I turned it over- one pic is the whole underside- the other is cropped to show 'it'

 

[diana a]

Looks like a sponge

 

[DYIguy]

Looks like a sponge

I have sponges- pineapple and one that looks like roots from a tree/ plant, but none with a center and 'fingers'- almost looks like a pink zoa/paly

 

[MadReefer]

I don't think its a sponge with spikes and a hole.