Trachyphyllia hitchiker?

[Belunn]

Hi
I just noticed some strange threads coming out from my Trachyphyllia. See attached image. Does anyone know what this is, and if it could be harmful?
I have had the coral for 3 years and it seems to be doing fine. I have not made any additions lately so wathever it is must have been there for a long time. The picture is taken in the night time so it only comes out when it is dark.
Does anyone know what this is?
Thanks!

 

[Tahoe61]

Looks like Mesenterial Filaments.

 

[LPS Bum]

Agreed. Those look like mesenterial filaments. Corals use these to engage in warfare with neighboring corals, to create space. Trachys normally aren’t super aggressive, but if you have anything within a few inches you’ll want to move it.

 

[Belunn]

Thanks for your answers! Seems like it is Mesenterial Filaments indeed. The coral above was completely burned for some cm closest to the Trachy last morning. Seems like it wants its own space :)