The stomatella snail (Stomatella spp.) often pops up in saltwater aquariums unannounced. And – depending on the species – it can cause confusion. Is it a slug? A nudibranch? Or is it really the snail everyone claims? You need to take a close look to appreciate these little gastropods. And since they’re determined members of the clean-up crew, you’ll be glad one (or more) showed up.
Table of Contents: Stomatella Snail
Stomatella snails are curious creatures. Not personality-wise. (They’re pretty narrow in their interests) No, we’re talking about their biology. They don’t resemble the standard image of a snail. It often prompts hobbyists to question whether they have a new pest in their tanks. But stomatellas deserve to hang out and help with algae control. And once you’ve skimmed through these links, you’ll understand why. (And maybe even appreciate them!)
- Common Names: Stomatella snail, Paper shell snail, Fingernail snail, Dove snail, Mini abalone, Shell-less snail, Slug snail, Top snail
- Scientific Names: Stomatella spp.
- Size: 1 inch (2.5cm)
- Minimum Tank Size: 5 Gallons (19L)
- Reef Safe? Yes
- Care or Experience Level: Easy
- Preferred Diet: Herbivore
- Original Part of the World: Indo-Pacific
At first glance, hobbyists spot stomatella snails and wonder how a common garden slug got into their tank. (Well, depending on the color of the snail) Because, unlike most snail species, stomatellas only carry around an itty-bitty shell. It’s a flattened structure in the middle of the body, topped by a thin layer of skin. And that makes it easy to miss. Especially on a snail so tiny. So, these snails are often victims of mistaken identity.
But stomatellas ARE sea snails. They belong to the Trochoidea Superfamily, which includes all of the species with gills and an operculum (the structure that closes the shell when a gastropod retreats inside). It’s a hefty group – in case the “Superfamily” label didn’t give that away – with over 2,000 species. And it’s a touch confusing. See, Trochoidea is ALSO the genus name of a LAND snail. (Makes you wonder why scientists couldn’t come up with a different label)
And the name-shuffling doesn’t end there. Most stomatellas pop up under Stomatella auricula. NOW, anyway. The species experienced a name change from Stomatella varia in 1997. But you can see different varieties out there. Not all snails are the shade of “neutral” you expect from a slug. You’ll see blacks, browns, greens, oranges, pinks, and reds. And that can cause hobbyists to mistake them for SEA slugs.
For instance, take a look at the stomatella in this YouTube video, happily crawling along through some coral (and try to spot the shell):
Stomatella snail shells are thin ovals similar in size and shape to your fingernail. (Hence why you see the other common name of fingernail snails) It’s still composed of calcium, as you’d expect from any snail. You just won’t see a large, elaborate creation. And the shell functions for protection as it would in any other gastropod species. The outer layer of skin over the top makes grabbing hold of the gastropod more complicated, though. For you or a would-be predator.
Stomatella Snail Lifespan
Stomatella snails pop up on reefs throughout the Indo-Pacific. Of course, picking them out from genuine sea slugs isn’t an easy task. You need to get close enough to spot that tiny shell. It takes a practiced eye. Mainly as NO ONE advises reaching out to touch a critter and feel for the covered shell. While stomatellas are harmless, plenty of the nudibranchs and sea hares out there AREN’T. You don’t want to risk injury
As with other snails, stomatellas “lay down” new rings on their shells as they grow. It’s an easy way to age the gastropods. Except you can’t see those rings on these snails. They’re pretty hardy as a species, though, living for around two years. A stomatella can even survive for a couple of months without food. Not that it’s recommended (of course). But it’s a nice testimonial to their sturdiness.
Creating the Ideal Stomatella World
While stomatella snails have a shell, it doesn’t provide the complete protection you see in other gastropod species. They need additional defense mechanisms. Which they DO have (we’ll get there in a minute). But when you’re a squishy, tasty morsel, it helps to live somewhere sturdy. That’s why you’ll find them in rocky structures throughout reefs in the Indo-Pacific. And it’s usually how hobbyists end up with stomatellas in their tanks.
The snails hide out in nooks and crannies within live rock. As adults, they don’t reach more than an inch (2.5cm). That means they can easily tuck themselves into a crevice. And with a neutral color palette, it’s easy for you to overlook a snail on your initial review of your new rock purchases. You won’t see the snails until they appear later.
But there’s no need to fuss since the live rock is the main element to keep your stomatella happy. The same hideouts they used to hitchhike into the tank will keep them safe within your tank. And they’ll have room to explore, forage, and rest. Additional rigid structures work, as well.
You WILL need to monitor your calcium and magnesium in the tank, though. It’s something easy to forget with the “submerged” shell of the stomatella. But they continue to build the protective structure under the skin. Ensure your calcium level stays between 380-450ppm. Periodic tests of your water parameters will help you stay on track.
If you purchase your stomatella snails, go slow with your drip acclimation. Invertebrates take twice as long as fish. And while the snail CAN navigate sand, it’s not the preferred substrate. You’ll want to set them on a rocky structure. Then wait. It’s normal for your snail to hide out (and refuse to move) for two days. Try another spot. If you get the same result a second time, you need to consider an alternative. (Such as heading back to the fish store)
Stomatella Snail Tank Size
At an adult size of just 1 inch (2.5cm), it’s tempting to pack in the stomatella snails. Particularly given their penchant for chowing down on algae. They’re compact and undemanding (except the usual invertebrate embargo on copper medications). But you still want to respect their spatial needs. And that means providing enough territory for each gastropod.
One stomatella needs 5 gallons (19L). It’s the general stocking rule of thumb for this species. You’ll ensure your snails have room to forage and explore without bumping into each other. And it’ll prompt you to stock enough live rock for everyone to get comfortable sleeping spots.
Are Stomatella Snails Reef-Safe?
As you probably already guessed, courtesy of the video above, stomatella snails enjoy crawling around corals as well as rockwork. And you’re free to let them. In their hunt for algae, the snails won’t bother, damage, or harass the coral in any way. Yup – completely reef-safe.
Considering stomatellas hunt down any algae they find, they’ll help improve the health of your reef tank. They’re beneficial members of the clean-up crew. And they won’t even bother your other invertebrates. (Unhappily, we can’t say the same for the reverse)
Stomatella Snail Diet
As with most (not all) gastropods, stomatella snails are herbivores. And their favorite selection from the menu? Algae. ANY algae:
If they happen across the plants in their foraging, they’ll stop and graze. And that takes potential pests OFF your worry list. It’s the best reason to allow the little hitchhiker to stick around in your tank (even if they’re not one of the more attractive colors).
Of course, once your stomatella wipes out your tank’s algae, you need to find some alternative food sources. But these snails aren’t picky. You can supplement their diet with nori or algae wafers. Add the greens to your tank twice a day. Just enough for the snails to finish the meal within a few minutes. (Same as you would for your fish or other invertebrates)
Stomatella snails actively hunt for algae. At night, anyway. While they happily scout around your aquarium, you’ll need to stay up late to catch them. These snails are nocturnal. It’s another way hobbyists miss spotting them in their live rock checks. The stomatella curl up during the day, waiting until the lights go out to slip out and explore.
As the diminished shell isn’t the most formidable protection, stomatellas have another defense against predators: Autotomy. Are you familiar with a lizard’s ability to detach its tail? The tail stays behind, twitching and confusing a predator. And the lizard makes a hasty retreat. That’s autotomy. Stomatella snails can do the same thing with a portion of their foot.
When cornered, the snail separates a piece of the foot. The dropped portion will spin in circles, attracting the predator’s attention. Meanwhile, the stomatella bolts for safety (and they’re FAST!). The foot then regenerates. It’s a way to compensate for the snail’s inability to completely retract into the shell (not to mention the fact they have sensitive flesh over the top of the shell!).
In general, you can keep stomatella snails with almost any fish or invertebrates. They’re peaceful gastropods. You won’t see them bother or irritate anyone. Unhappily, the reverse isn’t true. Some fish species find snails tasty. And the lack of a sturdy shell makes stomatellas irresistible. The same with certain invertebrates.
Even with that “escape plan,” your tiny snails can find themselves scooped up as the Special of the Day. You don’t want that. So, try to avoid mixing stomatellas with any of the following:
Considering their habit of devouring algae, who wouldn’t want to breed stomatella snails? And once you’ve learned to recognize the gastropods, you can introduce your hobbyist friends to the species. Luckily, breeding this snail isn’t tricky. In fact, all you need is more than one in a clean, healthy tank. The stomatellas will take it from there.
Now, yes, stomatellas are simultaneous hermaphrodites. But they can’t self-fertilize. That’s why you need more than one snail if you want to see any breeding. And you need to keep in mind that almost everything in your tank LOVES snail eggs. So, unless you plan to collect the eggs and raise them in a separate tank (or move the adults before they spawn), you’re probably going to lose most of the offspring. Have plans ready for their safety if you want to keep those tiny infant snails’ chances high.
Stomatellas spawn with the full moon – in the wild, anyway. In the aquarium, you’ll want to watch for your snails to migrate to the upper reaches of your tank and hang out for a couple of days. In the evening of that second day, they’ll release their eggs and milt. And you’ll see it. The water will turn cloudy (possibly REALLY cloudy, depending on how many stomatellas you have). It’ll clear as fertilization takes place. And when you check the tank again, you’ll see tiny pinpricks on the surface of the glass. Those are the new snails.
Once the snails hatch and mature, you’ll see the dots move around. Unhappily, they’re still vulnerable. It takes ONE MONTH for a stomatella to grow its shell. And until they have that layer of protection, they’re easy pickings for your fish and invertebrates. If you haven’t already shifted the tiny babies as eggs, consider moving them until they develop their shells. It’s easy to pluck them from the glass.
GLASS. If you try to remove a stomatella from a rock, you’ll hurt it. They attach firmly. And if you pull, you can remove part of the foot – permanently.
You can introduce the stomatella snails to your display tank or pass them on to new owners at a month old. They’re strong enough to hold their own at that point.
Not every hitchhiker is a welcome addition to a tank. Plenty of the invaders end up wreaking havoc once they gain a foothold in an aquarium. But even if you end up with happy reproducing stomatella snails, you shouldn’t see any problems. They don’t know how to make pests of themselves. And while they’re not always the most attractive gastropods out there, that’s not a reason to avoid them. Of course, there ARE some concerns with these little algae-eaters (no one’s perfect).
- Stomatella snails will eat any algae they find – including cyanobacteria, diatoms, and hair algae.
- As long as you have more than one stomatella, you can breed them (and then work on keeping the snail babies alive).
- Stomatella snails demonstrate autotomy, dropping a portion of their foot (which they’ll regrow) to distract a predator so they can escape.
- Stomatella snails are very active and reasonably fast, but only at night; they’re nocturnal.
- You can only attempt to remove stomatellas from glass. If you try moving them from rigid structures, you’ll cause permanent damage to their foot.
- Stomatella snails don’t acclimate to new aquariums well. You’ll need to use twice the drip acclimation time you’d use for a fish.
Not every hobbyist is familiar with the stomatella snail. And it’s not a big surprise as to why. They look like a slug when you see them for the first time (especially certain colors). It’s hard to decide whether the live rock hitchhiker should get to stay or not. But since the species happily devour the algae in your tank, it deserves the chance to stick around. (Snails are friends, too) And this unique little guy is just the thing your aquarium’s missing. But (as always) here’s some additional information – in case you’re still not sure about that sea slug-look alike.
This YouTube video provides a glimpse at an average stomatella snail (as you might expect to see it in your tank):
Want to know about some of the best stomatella snail tank mates?
Has the stomatella sparked an interest in snails? Why not consider some other species for your reef tank?
Not everyone’s a fan of snails, to begin with. And a snail that resembles a slug? That can take some getting used to. But stomatella snails are unique. They have a diminished shell under their skin. It’s not fancy or impressive, but it’s different from the average shell you see in most gastropods. And they balance that lack of protection with autotomy. While you don’t WANT to see that happen in your tank (it’s a tiny bit stressful), it’s kind of cool when it occurs naturally – in the wild. (And you can always bring the topic up at the dinner table)
So, if you see a stomatella appear after you add your next batch of live rock, consider letting it stick around. It’ll help with any algae that creep up. And it’s a nifty species not everyone keeps around.
What do you think? Do stomatellas deserve more recognition?
- Calfo, A. and Fenner, R. 2003. Reef Invertebrates: An Essential Guide to Selection, Care, and Compatibility.