From
The Reef Tank posted on January 27, 2010 21:12

Often, when I'm cleaning my aquarium, I run into bristle worms. The first time I ever found them in my aquarium, my mind ran wild with the evil things these foreign looking worms could do in my aquarium. They can be kind of freaky to run into if you've never dealt with them before, but before you panic there are a few things to consider.
First of all, what is a "bristle worm" exactly?
You might have seen pictures or heard of them before, maybe you've even dealt with them directly. "Bristle worm" is a term that casually describes many types of worms in the class of marine worms referred to as Polychaeta. They are segmented and they have bristles. Good stuff.
The bristle worms that aquarists need to watch out for, in general, are the ones referred to as Fireworms. These worms usually appear in your aquarium as red, segmented and bristle covered. They can range greatly in size, from being so small that you need a tweezer to handle them, to being several inches or more in length. You might only see them at night, at least that's the only time I see them in my aquarium.
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