Any ideas what this is on my Lobo?

[ReeferMadness80G]

It's white and stringy and has started appearing at night and it's gone during the day.

 

[scobeyra]

I usually see those when it's fighting with a nearby coral. Defense. Something close besides those Zoas?

 

[ReeferMadness80G]

I usually see those when it's fighting with a nearby coral. Defense. Something close besides those Zoas?

That's actually a favia, but no other corals are close.

 

[Tahoe61]

Those are mesenterial filaments, used as a defensive mechanism and in some corals a digestive mechanism. It is odd as to why they are protruding from that area of the corals. These internal structure often appear from the oral opening in a response to near by corals, or changes in water chemistry. Typically corals will display filaments at night. The favia may be extending them as well. Unless the coral in question begins to show tissue regression the presence of filaments would not concern me, but I would move those two corals farther apart.