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Spirorbid worms | Aquarium Friend or Foe?

If you’ve been following the FantaSEA blog for a while, you’ll know that there are plenty of critters out there that can show up in your aquarium uninvited. That’s why we’ve got the Aquarium Friend or Foe section! Today’s creature feature: spirorbid worms. Are they useful guests or unwanted pests?

Keep reading for everything you need to know about spirorbid worms in the aquarium.

What is a spirorbid worm?

Spirorbid worms lend their name from their genus: Spirorbis. They’re tiny polychaete worms (a large class of segmented worms with bristles protruding from their body). What sets them apart is their white spiral shell, which makes it easy to confuse these guys with snails. After all, these tubeworms only pop out to eat! The different species of Spirorbis naturally occur in relatively shallow waters, where they can be found clinging to any surface they can find, notably seaweed.

Spirorbid worms are very common aquarium hitchhikers. Whether they enter your tank on live rock, a coral frag, or something else: it’s almost impossible to completely eliminate the chances of these guys popping up in your marine tank.

Are spirorbid worms aquarium friends or foes?

We’re happy to report that they’re friends. Like many of the other hitchhikers we’ve discussed, such as pineapple sponges and Stomatella snails, spirorbid worms are tiny filter feeders that really don’t harm anything. In fact, they’re a nice little help to your aquarium’s filtration system.

We know these guys can be a bit unsightly, so we’ll include ways to reduce the population below. You don’t want to end up unable to see your fish and corals due to the aquarium viewing panes being completely covered with little spiral shells, after all. Additionally, a spirorbid worm overload can signal an imbalance in the water, something that can eventually lead to additional problems if you don’t take measures.  

All that being said, we do leave these guys alone if they’re in a place where they’re not visually annoying. They’re absolutely welcome to do their useful work in our tanks’ sumps, for example!

Spirorbid worms | Aquarium friend or foe?

How to reduce spirorbid worm populations

In some unlucky cases, you might end up experiencing a massive spirorbid worm population explosion. This can happen in new tanks that are just settling in, though overfeeding is another common cause. These filter feeders love dusty powdered coral foods and any other small particles they can catch, after all. You may also have overstocked your aquarium, giving the spirorbid worms plenty of fish waste to feast on.

So what can you do? You should be able to scrape spirorbid worms off the aquarium glass. It’s a bit more difficult on rock, but still, you can consider taking décor out of the tank to give it a scrub. These are temporary solutions, though: if you don’t solve the underlying problem of excess nutrients being present, the critter population will just creep back up over time.

Make sure you do regular aquarium maintenance. Check whether you’re overfeeding and if you may have added too many fish or invertebrates to the tank. If this is the case, adjust accordingly and you should eventually start to see the spirorbid worm numbers start to decline. 

Because these are tube worms that rely on their hard shells for protection, there aren’t really any effective predators out there that can be of much help in taking them out. Some aquarists recommend six-line wrasses, but these are definitely not suitable for all types of tanks, so you’d have to check beforehand whether they make a good fit. Hermit crabs might also be somewhat useful, but remember that there’s no guarantee any critter will prove helpful. Solving the usual underlying issues is a better bet in most cases.


A beautiful aquarium can really tie a space together, but all tanks do need some specialist knowledge to make sure they stay healthy. Learning about all the potential hitchhikers you might encounter in a saltwater aquarium is almost a science by itself! 

If you don’t have time to become an aquarium guru, why not let us help you design, set up and maintain your tank? Contact us here with your ideas and we’ll get back to you soon.

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Marijke Puts

Hey! I'm Marijke, FantaSEA's resident blog writer. I'm a full-time pop science author, part-time PADI diver and snorkeler, and have been keeping fish since I was a kid. When I'm not writing fish care guides, you can usually find me underwater or trying to figure out how to fit more tanks into my house.

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