I got some live rock yesterday, and small worms poked their heads out. The worms are about 2mm thick and about an inch long. Half of the worm is red and the other half is black. Is this a fire or a bristle worm?
Without a pic it is just a guess, but my guess it is just a normal bristleworm. I have always read about the "dreaded fireworm" but in all my years of working on tanks in my area I have never seen or even heard from anyone else locally or online about anyone actually finding a real fireworm. So just going off 17 years of experience I have to say the chances of actually getting a true fireworm are very slim, although not impossible.
This is what a true fireworm looks like. Very distinctive and after seeing thousands of normal bristleworms in my time it would be very easy to tell the difference if I saw one that looked like this.