Weird mat of red worms?

[StrombusEyes]

This came attached to a rock with GSP. It’s got lots of holes and at night red filaments (?worms) come out but during the day the purple parts cover them.
Never seen anything like it

 

[StartingATank]

Wow that is interesting, I would think it is a type of coral but it looks very strange. Will be following

 

[thamnasteroid]

Tunicate

 

[ISpeakForTheSeas]

Tunicate

+1 colonial tunicates; I'm not sure what the red stuff is; the purple might be early sponge growth. The tunicates are technically harmless/good to have, but some colonial species can become invasive to the point of growing over and smothering corals, so I usually recommend isolating them in a spot where it's easy to manually control any spread.

 

[thamnasteroid]

Tunicate

+1 colonial tunicates; I'm not sure what the red stuff is; the purple might be early sponge growth. The tunicates are technically harmless/good to have, but some colonial species can become invasive to the point of growing over and smothering corals, so I usually recommend isolating them in a spot where it's easy to manually control any spread.

I believe the purple is also part of the tunicates

 

[ISpeakForTheSeas]

I believe the purple is also part of the tunicates

It might be; I'm not sure because of the patches without it on the tunicates and the patches of it without the tunicates visible growing on the coral.