What is this caterpillar thing in my tank?

[Mal]

Does anyone know what this is? What do youknow about it?

 

[Mal]

Anyone ever see these? I have many of them in one of my tanks. They [many of them] mostly come out at night. Sometimes you see one during the day.

Mal

 

[wade1]

Its a species of bristle worm. Perfectly normal part of the biota that controls detritus and leftover food in the tank. They are a good thing to have around as they will not only remove waste from the sandbed, but also oxygenate the upper layers (although with CC that isn't really an issue).

For helpful images and descriptions, see the hitchiker faq:
http://reefs.org/hhfaq/

Wade