What could it be?

[Chris444]

Hi, is anyone able to identify what is next to my mushroom?
Looks transparent and there is plenty of it for such a small frag.
The mushrooms seems not happy for few days. I cant see them anywhere else

 

[Crabs McJones]

Tube sponges. Harmless filter feeders. If they bother the coral you can scrape them off, but they generally dont