Aiptasia and flatworm?

[BubblesandSqueak]

Two ID’s while cleaning up some GHA today. Found something that looks like a snail out of its shell and not the typical Aiptasia I’ve found. Is this a giant flatworm? It’s in the rock and I’ve never seen it crawling around the tank. Guessing 1.5”.

 

[hers0109]

First pic looks like a sponge to me but there are others who are more expert on pests who can chime in