Ahhh...so many...video included

[Erink]

These little guys keep popping up. I do have 1 brittle star for sure, possibly 2. They start super skinny and tiny then get this size... about 1/2".

 

[Scottmac]

It looks like the arms of a brittle star. I am in the process of setting up my first marine tank, and the live rock I have added looked like this with wavy spiky banded tentacles I first assumed to be worms, but this is what brittle stars do during light hours. They nestle in the rock with their arms partly out to catch the odd particle, then come out fully in darkness. V beneficial.

 

[Erink]

Yeah, I have a few brittle stars that come out but these are different. They are only one though. They look different like a worm

 

[Bfragale]

Could be a bristle worm, but looks like a leg of a brittle star. As long as it’s not red(fire- bristle work), shouldn’t be a problem.