Sponge? mesentrial filaments? Spaghetti worms?

[MikeReefs]

Trying to figure out what’s coming from this hammer coral. Whatever it is it doesn’t seem to bother it. They don’t move but seem to be colonizing this part of the rock and frag plug

 

[Crabs McJones]

Are they hard or soft? Sort of looks like fan worm tubes

 

[Cthulukelele]

Regardless of what they are (which is hard to identify in a blue photo like this one) something that looks like that is almost always beneficial and not a danger to the tank if that's helpful for your sanity.

 

[GSPClown94]

Are they hard or soft? Sort of looks like fan worm tubes

That’s also what I’m seeing. White light pics would be easier to see stuff in.