nassarius snail

Nassarius snail

The nassarius snail, N. vibex, is a small member of the mollusk phylum and is a fairly common addition to the saltwater aquarium as part of the cleanup crew. They are amusing to watch. By day, they bury themselves in the sand, with just a tiny periscope-like piece of flesh left sticking out of the tank.

nassarius snail

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When you feed your fish, you’ll think you rang a dinner bell, because these snails will come crawling out from the sand bed like zombies from the night of the living dead.

But are they really an essential part of the reef cleanup crew? That appears to be where the controversy about this snail resides.

If you plan to keep them in your tank, you should have a deep sand bed. These critters aren’t really appropriate for a bare bottom reef tank.

Nassarius snails (or pretty much any snail, for that matter), are not compatible with hermit crabs, because those arthropods may prey on the mollusks, turning them into escargot and turning their shells into a mobile home.

What do Nassarius snails eat?

If you’re like me, I think of snails as being useful to keep the problem algae population of my tank down. But that’s not the case with the nassarius snail. These snails don’t eat algae they eat carrion, which is a fancy word for dead fish. That’s right, not only do they crawl out of the substrate like a zombie, but it also has a craving for flesh, not algae. To that point, they may be somewhat useful in cleaning up uneaten meaty foods left in the aquarium, like Mysid shrimp or brine shrimp.

Do Nassarius snails eat other snails?

No, they are scavenging, carnivorous mollusks that eat dead carcasses, not other living snails.

Will Nassarius snails eat diatoms?

No, Nassarius snails are scavenging, carnivorous mollusks that prefer to eat dead carcasses (kind of like tiny, underwater vultures…with shells…ok that was a stretch). They will not eat diatoms. If you are looking for a snail that will eat diatoms, check out Nerite or Trochus snails. Because they stir up the sand bed, they may indirectly make it more difficult for diatoms to grow on the sandbed.

How big do Nassarius snails get?

Nassarius snails are small and grow only to about a half-inch in size when fully-grown.

Nassarius snails poisonous?

No, Nassarius snails are not poisonous.

Are Nassarius snails nocturnal?

Nassarius snails are generally much more active at night, although they will emerge from the sand when they smell food.

Do they need sand?

Nassarius snails burrow into a substrate when they are not active, so you should have some sort of soft substrates like sand or mud.

Do they breed in captivity?

Aquarium owners report and post that a happy group of snails has laid eggs in their tanks (on the aquarium glass, for example), but this is a very difficult species to raise in captivity. The most likely result is that they’ve created a natural zooplankton bloom in your tank, feeding some of the other invertebrates (or fish). The eggs generally hatch after a few days (~3-5).

Are nassarius snails useful?

That depends on what clean-up-crew role you need help with. Nassarius snails are not that useful in getting rid of problem algae, but if dead fish carcasses or too much meaty food, rotting in your tank are your problem…then, yes, they are useful. They are also very useful in stirring up the sandbed, keeping oxygen levels high in the substrate.

second nassarius snail

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In all seriousness, the nassarius snail can be a bit helpful. The fact that these cleanup critters zoom out from the sand bed at the first sign of feeding your tank is a signal to me that they will and do eat excess (I assume meaty) foods.

The challenge with keeping them in your tank is that they may help clean up excess meaty foods, but if you don’t have a lot of excess food (probably a good thing) they may starve.

Can Nassarius snails right themselves?

Yes, they are quite adept at righting themselves if they fall over. They do this by changing their center of gravity by stretching as far as they can out of the opening in their shell.

Are they part of my cleanup crew?

In the past, I have added them to my tank, but I do not have them in my tank currently.

For more information

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Check out these carrion eaters in action:

How many Nassarius snails do I need?

It is difficult to give a one-size-fits-all recommendation about how many Nassarius snails you might need for your aquarium, but the answer is certainly: not many. Their primary food is a dead fish carcass, which, you should generally not have a lot of, in your fish tank. As such, most tanks would likely not need more than a few (3-5), perhaps more for very large tanks.


Nassarius snails are:

  • inexpensive
  • peaceful and easy to add to any tank with a sandy substrate
  • interesting to watch
  • possibly helpful
  • certainly not an algae eater

For further exploration, I would be interested to see if adding these carrion-eating snails helps to keep bristle worm populations in check, but competing for the same food. I don’t have research to support that, I’m just hypothesizing. So if you absolutely hate bristle worms, that may be another reason to try them.

If you were interested in this snail because you thought it would help you with problem algae, I encourage you to check out trochus, turbo, or Astrea snails, instead.

Written by Albert B. Ulrich III–author of The Reef Aquarium Series of books:  The New Saltwater Aquarium Guide, How to Frag Corals, 107 Tips for the Marine Reef Aquarium

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