White stuff on mushroom coral, parasite? Guts?

[YukiFung]

Dear all,

Any idea on the white stuff attaching the mushroom Coral?

The coral was introduced into the tank for a couple of days.

I can’t see they moved if they are parasites.

They just randomly appear and disappear on the corals.

Thanks

YukiFung

[AlSimmons]

They might be Mesenterial Filaments. (basically the corals guts) Sometimes these are used as a defense mechanism, other times it could just be an indication that the coral is a little stressed out at the moment.