The Bristleworm- Friend or Foe?

Ask ten people in the hobby about bristleworms and odds are good that at least half of them will tell you that they are terrible, horrible creatures that will kill your fish and eat your corals. There are a lot of opinions on these lowly creatures, and I have always argued that anyone that tells you that they are villains has resorted to judging a book by its covers (or a worm by its slime and spines) and overlooked how useful these guys really are. 

First of all, for those of you who don't know, a bristleworm is a common critter to find in any reef tank squirming its way through the sand and rocks in a never ending quest for food. There is no denying that they are not the most handsome of creatures, something which prevents many people from seeing their true beauty. Look upon the loathsome bristleworm and shudder!


Even this fuzzy nighttime picture doesn't do this guy any favors, there is no denying it. So why am I such a fan of bristleworms?

First of all a small disclaimer, I like all kinds of creepy crawlies and gross critters so I am predisposed to be partial to them and give them a pass that some people might not. BUT even if I wasn't a weirdo like that I would still argue for them, and here is why:

  1. Despite what many people think, they don't eat your livestock. If you see a bristleworm eating something in your tank it was already dead or close enough to have made no difference.
  2. They are free clean up crew. In the world of saltwater tanks the clean up crew is a vital piece of biological tech we have at our disposal, but all the hermit crabs and snails in the world won't get everything and they certainly won't eat all the stuff the various worms in our tank do. Bristleworms are free, repopulate themselves, stay hidden most of the time, and eat things that we don't want lying around our tanks.
  3. Liverock and substrate needs to be maintained. These guys get into places that almost nothing else can and they keep those areas free of detritus that would otherwise buildup and create nitrates and phosphates. No one wants those things getting out of hand!
  4. They help maintain the ecology of your saltwater tank. Of all the worms you want in your tank, these guys are the top dogs. They keep the other ones in check and prevent population booms of other critters.

Of course just like anything bristleworms have their cons as well. They can get out of hand if your tank isn't maintained properly and too much food is introduced to the tank, leading to these guys getting out and about more which most people don't enjoy. Also, touching them is painful so that is best avoided. Their close cousin the fireworm is downright dangerous, but thankfully it isn't often seen in home aquaria nowadays. 

So the next time you see the lowly bristleworm sliming its way through your tank late at night or in the evening look the other way and let it do what it does best. Or take a moment to marvel at an evolutionary powerhouse that has been keeping the world's oceans clean for millions of years and will do the same for your tank for as long as you have it.