|They will kill it with FIRE!|
You may not even know how you got a Hawaiian Lined Fireworm in your tank, or if the worm’s whole life goal is to devour your coral, or fish, or Jeffery, and you may not even know what they look like. Actually, you may not even know you have one until you’re peering into your tank one night with the lights off observing your coral to see if they’re opening properly to feed. Chances are if you have live rock from Hawaii you have one of these precious but freaky little fellows in your tank.
Never fear, here is all the information you need to know about these prickly little worms. First of all they have a scientific name that is way cooler than their common name, it's Polychaete. Pretty neat huh? They are a class of annellid worm which does not sound as cool as Polychaete, and you probably don't even care. There are 10,000 different kinds of these little worms, but we only care about the Hawaiian Lined Fireworm. These little buggers get to be about three inches long if they have the right conditions in your tank; or larger, but they won't reach the size of those other Polychaete that can get to over 9 feet in length. As an aside they're related to your colorful little friends the Christmas Tree Worm and feather dusters. That immediately rockets them up the cool scale, even if they are the creepy cousin.
Hawaiian Lined Fireworms can and will sting you, if you touch them, though I don't think anyone is quite dumb enough to try and touch something that looks that prickly because your brain will tell you "Hmm that probably hurts". They can also sting other things in your tank, which they probably won't, because the other things in your tank are going to think the same thing.
These bristle worms will not eat your healthy coral, so don't believe the schmuck that tells you they will. The only time they will even approach your coral is if it is already dying, and then like any reasonable member of your cleanup crew they will begin to feast on it. Otherwise they will hang out in your rocks and only appear when the lights are off, or when you're feeding your fish something meaty like krill. We usually see ours peek out when we're feeding Juan Pedro and he's really going to town, or if we're target feeding our coral at night. We've never seen our Hawaiian Lined Fireworms approach our coral even curiously, as they're much more focused on patrolling our rock and substrate for food.
Now, if you're feeding your coral and fish regularly you probably have three or four Hawaiian Lined Fireworms and they are probably about an inch long. If you're overfeeding your fish and coral you're going to have upwards of twenty and they're going to be big. They're actually a very neat cleanup crew member because they self regulate by staying small and dying off depending on the food supply. You'll probably always have one or two, but if your population gets out of control you might want to start removing a few with tweezers (you jerk) and cut back on the feedings. Being omnivorous they will eat algae and any spare bits of meaty foods. They're also free, because they come as hitchhikers, which makes them a very thrifty alternative to buying lots of Jeffery to take care of the tank. Your Hawaiian Lined Fireworm will not climb on the glass, he's a rock man, which is fine. He'll patrol all those little nooks and crannies you can't reach.
Some of you may be wondering, "But what about my precious Jeffery!?" First of all, screw your Jeffery, second while the Interwebs will tell you that the bristle worms will eat your snails (and some may!) the Hawaiian Lined Fireworm thinks your Jeffery taste like crap. In fact he will only approach a dead Jeffery, and then do you really care? I don't, and so you shouldn't care either. Think of the Hawaiian Lined Fireworm as a hyena, not a lion. He won't hunt down and slaughter your Jeffery, your coral, your fish, your nudibranches, or anything else for that matter...but he will gladly feast upon their dessicated remains.
To sum up, he should be a welcome hitchhiker, a cool addition to your already fantastically neato tank. He will grow based on his food supply and reproduce accordingly, he won't destroy anything, but he will sting you if you touch him so exercise a little caution and don't think about picking him up to put on a leash and go for a walk around the block with. Think of him as the neatest mini-meme, because he will kill it with fire, Fireworm style.