Are there pests that eat Euphyllia base?

[W0terMoist]

Bought this gold octospawn from my local shop. Brought it home and gave it a dip. Saw these indentations on it and found a small and hard flatworm crawling on the plug.

Are there pests that eat the base of corals?

 

[reddogf5]

Are there pests that eat calcium carbonate? I doubt it, that's more work for less nutritional value than eating plain celery.