What is this on my Duncan?

[DebFerreira]

This Duncan is in a 13.5 nano with stock lighting kept on blue (except for this pic) plus two smaller blue LED supplemental lights. I just noticed this today.

 

[rhostam]

Those are mesenterial filaments. The guts.

When Corals Spill Their Guts

One of the more common and often more disturbing observations for many newer reef hobbyists is seeing their corals extend their mesenterial filaments. Reactions

reefs.com

 

[DebFerreira]

Thanks for the reply, and the link. I was worried that it had some sort of terrible infection.