Good or Bad Bristleworm

[sffinn01]

So I've been doing a blackout for my dinos that I'm trying to keep dosing with H2o2 and checked on it today and saw this little guy and was curious if it was an ok bristleworm or a bad one. Also I was curious about the white spider web looking thing on the sand bed. Thank you so much and sorry if the picture is bad he started hiding when I brought the flashlight out.

 

[Dbichler]

Looks like a bristleworm they adjust in numbers to amount of food available.

 

[Gtinnel]

The picture is too blurry for me to tell, can you get a better picture or has the worm already gone back into the rockwork? Unless you have actual live rock that was added to your tank its most likely not harmful.