Help identify this

[jofra]

Tonight, looking at my aquarium, I saw that there are these white things on the trunk of a euphylia. What is this thing? I don't know if it's some kind of sponge or worm.

 

[Reefing_addiction]

Tonight, looking at my aquarium, I saw that there are these white things on the trunk of a euphylia. What is this thing? I don't know if it's some kind of sponge or worm.

I would think sponge

Also reminds me of what mercury does to aluminum