Identification of Marine Eggs

Cerith Snail Eggs

A single dot, a squiggle of white, a floating orange ball – marine eggs come in all shapes, sizes, and colors! Of course, the easiest way to tell what it could grow up to be is to find mom nearby, but that’s not always possible. These are just a few of the most common eggs found in an aquarium to help you with the identification of marine eggs.

Berghia Nudibranch Eggs (Berghia verrucicornis) – Reef Safe:

Berghia Nudibranch Eggs

Anyone plagued by Aiptasia sp. anemones needs to know about Berghia nudibranchs. These nudibranchs only eat Aiptasia anemones, and they produce an egg sac like the one pictured every few days. Below, a microscope image shows the developing nudibranchs, along with grown adults.

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Nerite Snail Eggs (Nerita sp.) – Reef Safe:

Nerite Snail Eggs

Nerite snails are a great snail, but I only know of one person who had nerite eggs hatch and grow successfully to adults (in other words, most eggs do not become adults…or even make it to juveniles.) The eggs look like white sesame seeds and are sometimes found singularly or in small groups (like the four in the photo below). Read more about snails here!

Nerite Snail with Eggs
Nerite Snail with Eggs

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Collumbellid Snails…AKA Hawaiian Strombus Snails…AKA Strombus maculatus – Reef Safe:

Collumbellid Snail Eggs

Ok, so maybe the taxonomy isn’t entirely straightened out on this snail yet, but regardless of name, they’re great snails. As you can see by the multiple egg sacs, they reproduce faster than rabbits. If you’re sick of buying snails, then these are your best choice in my opinion. They graze over rocks and on glass, stay small, and their population waxes and wanes with food supply. Read more about snails here!

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Nassarius Snail Eggs (Nassarius sp.) – Reef Safe:

Nassarius Snail Eggs

Nassarius snails produce various egg patterns, depending on species. Some of them produce some of the most beautiful “fan” patterns of marine eggs, but others leave these small individual sacs. Read more about snails here!

Tonga Nassarius Snail
Tonga Nassarius Snail

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Cerith Snail Eggs (Cerithium sp.) – Reef Safe:

Cerith Snail Eggs

Cerith snails are a beneficial part of a reef tank clean-up crew. They reproduce in captivity to some extent (some aquarists have more success than others, and the juveniles make it to adulthood in small numbers). The egg pattern is very distinctive, as shown with the
mother (and possibly father). The egg pattern will vary by species, but most have something similar to this white swerving pattern or the fuzzy white string below. Read more about snails here!

Cerith Snail Eggs

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Stomatella Snails (Stomatella sp.) – Reef Safe:

Stomatella Broadcast Spawning

Stomatella snails are hands-down my favorite snail. They come in nearly all colors (like the black one and speckled one below, but also in red, silver, green, etc.) They frequently enter an aquarium as a hitchhiker, scour the tank for algae, and then reproduce prolifically. They’re broadcast spawners, so they reproduce by climbing high in the aquarium and releasing small puffs of sperm and eggs which look like smoke.

Although the stomatella snail can’t be seen in the photo with the Scolymia coral, there is one hiding under the coral releasing either sperm or eggs (white smoke-looking mass to the left of the
Scolymia). This event lasted about 3 minutes. Unfortunately, I’ve had a hard time determining their life cycle times since they constantly have new batches of babies. Read more about snails here!

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Conch (Strombus sp.) – Reef Safe:

Queen Conch Eggs

I had (what I assume to be) a mated pair of fighting conchs that regularly laid eggs. Unfortunately, I never had success raising these in captivity. Read more about conchs here!

Conch
Conch

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Acropora-eating Flatworms (Amakusaplana acroporae) – Not Reef Safe:

Acropora Eating Flatworm (AEFW) Eggs

As the common name implies, these flatworms only eat Acropora corals. Although they usually lay their eggs directly on the Acropora corals, the eggs can sometimes be found near Acropora corals, like on a frag plug in the photo.

Acropora Eating Flatworm (AEFW)
Acropora Eating Flatworm (AEFW)

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Polyclad Flatworm – Not Reef Safe:

Polyclad Worm Eggs

These massive flatworms are not reef safe due to their predatory behavior. I found one of these flatworms inside a hole in the live rock attached to a coral along with the marine eggs shown. Although I am not 100% certain the eggs are from the flatworm, there were no other large invertebrates within the live rock. Additionally, the eggs resembled very large Acropora-eating Flatworm (AEFW) eggs, another polyclad flatworm species.

Polyclad Worm
Polyclad Worm

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Gall Crab Eggs – Reef Safe with Caution:

Female Gall Crab

There is quite a bit of debate over whether gall crabs are reef safe, but I, personally, have not experienced any issues. The female builds a small hole in live rock, and corals grow around the crab. Since sick corals often contain gall crab inhabitants, the crabs are often blamed for the coral’s ill health. I should note that extremely large, healthy corals in the wild house gall crabs with no noticeable problems. The female shown is carrying eggs (in yellow).

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Coral Eggs – Reef Safe:

Tubastrea Coral Eggs

Coral eggs, like the Tubastrea coral eggs shown, are typically orange balls. The coral below actually started spawning while in a coral dip!

Tubastrea Coral Eggs
Tubastrea Coral Eggs

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Unknown Marine Eggs

Unknown Marine Eggs

Marine egg diversity is vast, as shown by another pattern here. What eggs have you found in your tank?

Identification of Marine Snails

Conch

Marine snails come in all shapes, sizes, colors, and function, so proper identification is crucial! These marine snails are some of the most frequently available or commonly seen.

Astraea sp (Astrea Snail): Reef Safe

Astraea

These snails annoy me the most – so much so that I have to question how they aren’t extinct. They frequently tip over and have no ability to right themselves, thus being easy targets for predators. I would avoid this snail unless you have enough time to flip each one back over constantly or enough money to keep buying more.

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Cerithium sp. (Cerith Snail): Reef Safe

Cerith Snail

Cerith snails are a beneficial part of a reef tank clean-up crew. They reproduce in captivity to some extent (some aquarists have more success than others, and juveniles typically make it to adulthood in small numbers). The egg pattern can be very distinctive (depending on species), as shown below. Exact species identification of this marine snail is challenging, as the patterns, shell structure, and anatomy vary so little. Knowing the exact origination region may help.

Click to learn more about identification of marine snail eggs!

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Collonista Snails: Reef Safe

Collonista Snails

Most reefkeepers have probably run across the Collonista snail at some point or another – likely as a teeny speck of a snail on live rock or on the glass. These reproduce in captivity faster than the Columbellid snails in my experience, and it isn’t unusual for them to just about cover every surface at night. For whatever reason, I rarely see them grow larger than a pinhead, but I have had some grow over the years to about the size of a pea.

Some hobbyists confuse these as baby Turbo snails or baby Nerites, but they are a separate species. Again, the proper identification of marine snails is important, as these can become a nuisance since small size allows them to clog pumps

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Collumbellid Snails (Hawaiian Strombus) (Strombus maculatus): Reef Safe

Collumbellid Snail

Ok, so maybe the taxonomy isn’t entirely straightened out on this snail yet, but regardless of name, they’re great snails. As you can see by the egg sacs below, they reproduce faster than rabbits. If you’re sick of buying snails, then these are your best choice, in my opinion. They graze over rocks and on glass, stay small, and their population waxes and wanes with food supply.

For more information on Collumbellid snails, read on here!

Click to learn more about identification of marine snail eggs!

Collumbellid Eggs
Collumbellid Eggs

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Strombus sp. (Conch): Reef Safe

Conch

If you are looking for a snail with a bit of a personality, then I suggest a conch. They often submerse themselves below the sand with an eyeball or two sticking up to watch their surroundings. They’re great algae-eaters and sand-sifters. I had (what I assume to be) a mated pair that regularly laid eggs. Unfortunately, I never had success raising these in captivity.

Click to learn more about identification of marine snail eggs!

Note: Strombus alatus (“Florida Fighting Conch”) and “Tiger Conch” are pictured.

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Melongena corona (Crown Conch): Not Reef Safe

Crown Conch

Despite the fact that this conch was photographed in front of some zoanthids, this conch is not considered reef safe. They are mollusk predators, and they may even be cannibalistic. Unfortunately, my identification of marine snails as a newbie to the hobby was pretty poor when I bought this conch. Live and learn!

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Monetaria annulus (Money Cowrie): Reef Safe

Money Cowrie

This fairly small cowrie is reef safe, as it eats a variety of film and hair alga across the tank.

*Note: This cowrie was previously named Cypraea annulus.

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Nerita sp. (Nerite Snail): Reef Safe

Nerite Snail

Nerites are my first choice to purchase. Nerites lay eggs very frequently (small white dots), but unfortunately, I only know of one case personally where a hobbyist was able to get the eggs to grow to adulthood.

The only downside to these snails is that they prefer tidal zones, so they will hang out toward the top of an aquarium. I’ve found quite a few that managed to escape before, and it’s not pleasant. If you need snails to clean your rocks, you may find the Ceriths or Stomatella snails of interest.

Click to learn more about identification of marine snail eggs!

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Stomatella Snails: Reef Safe

Stomatella Snail

Stomatella snails are one of my favorite hitchhikers. They often come in on live rock or corals, and do well in the home aquarium. But best of all, they reproduce in captivity and will fill an aquarium with babies relatively quickly if there is a lack of predators. Their shell is shaped like a fingernail, which leaves them vulnerable to hermit crabs and other predators (however, they can lose their tail like salamanders can in self-defense). They’re most active at night, and it is not unusual to find them perched on a high rock in the middle of the night releasing what appears to be small puffs of smoke (they’re broadcast spawners.) If you’re looking for an active day-time snail, Ceriths and Nerites are good options.

Click to learn more about identification of marine snail eggs!

Black Stomatella Snail
Black Stomatella Snail

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Astraea phoebia (Ninja Star Snail): Reef Safe

Ninja Star Snail

I occasionally see these for sale, and of course, I shelled out the extra cash for a “really cool looking snail”. In my opinion, they’re neat, but not worth the extra expense. I am not aware of their reproductive capability in captivity.

Ninja Star
Ninja Star

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Vermetid Snails: Reef Safe with Caution

Vermetid Snail

Vermetid snails are one of my worst enemies. They are stationary snails as adults and build permanent tube structures on the reef. To catch food, they extend a sticky mucus strand and reel it back in to eat the particles. They aren’t exactly harmful to a reef, but the mucus strands may annoy corals and detract from their physical appearance. And, while they may not be harmful to a reef, they are harmful to soft skin! Picking up a rock with these sharp tubes may cause significant pain/injury and even infection. Use caution when working around these hitchhikers.

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Nassarius sp Snails: Reef Safe

Tonga Nassarius Snail

Although Nassarius snails are reef safe, there are whelks (predatory snails) that look very similar. Nassarius sp. are great sand-sifters, and they have an amazing sense of smell. Within seconds of adding food to an aquarium they will surface from the sand and head straight for the food.

Click to learn more about identification of marine snail eggs!

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Turbo sp. (Mexican Turbo Snails): Reef Safe

Turbo Snail

These are the bulldozers of the snail family for a reef aquarium. They grow very large and have voracious appetites to match. Not surprisingly, they are not graceful creatures and will bump rocks and corals over. Beware of these snails if you have an overflow as well. Their shell diameter seems just perfect for clogging plumbing and allowing tanks to overflow. (Yes, it happened to me!)

Many aquarists believe Collonista snails are juvenile turbo snails, but they are a separate species. I have not had success with turbo snail reproduction.

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Turbo sp. (Zebra Turbo Snails): Not [Typically] Responsibly Reef Safe

Zebra Turbo Snail

Do you see the Nerite snail to the right of the Zebra Turbo snail? That Nerite is nearly an inch long, for scale. Unfortunately, small Zebra Turbo’s are sometimes sold in the hobby and marketed as great cleaners (which they are!) But, they can become massive bulldozers! This is another example of why proper identification of marine snails is important. These should remain in the wild, or only collected for the absolute largest aquariums. (Sure, there may be some smaller varieties/species than the one shown here, but still, most become bulldozers if they do not starve to death first.)

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Scutus antipodes (Elephant Snail): Reef Safe

Elephant Snail

Although they are generally considered reef safe, as their name implies, there are reports of massively-sized ones in the wild. The ones encountered in the hobby may be a smaller variety. They are members of the limpet family, and they sometimes show a glimpse of their white shell on their back (as shown below).

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Zig Zag Periwinkle Snails: Reef Safe

Zig Zag Periwinkles

These small snails (about half an inch, maximum), eat algae, diatoms, and detritus throughout the tank. They’re hardy, but I have never had success with their reproduction.

Zig Zag Periwinkles
Zig Zag Periwinkles

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Dwarf Planaxis Snails: Reef Safe

Dwarf Planaxis

These are neat reef-safe snails that may even clean in the sand under your rocks. Unfortunately, I’ve never had success with their reproduction.

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Pyramidellidae (Pyramidellid Snails): Not Reef Safe

Pyramidellid Snails

These extremely tiny parasitic snails are shown on the underside of an Astraea snail. Although they typically infest clams in the home aquarium, they also can infest the snail population.

Unfortunately, these came in on a single snail, and then they spread to nearly every snail in the tank. I tried to remove them manually, from every good snail, but I simply couldn’t keep up (or find every single snail every single day). Although I lost all of my snails, the outbreak was contained to my quarantine tank.

I highly recommend lightly scrubbing snail and clam shells, prior to placement in a quarantine tank. So not only is identification of marine snails important, but so is quarantine and observation! The scrubbing can remove adults along with egg masses, and quarantine will allow you time to monitor for any additional adults. However, if some slip by, some wrasse species may help keep the population under control (although, they will probably not eradicate the population since these snails are experts at hiding).

Pyramidellid Snail
Pyramidellid Snail

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Cyphoma gibbosum (Flamingo Tongue Snail): Not Reef Safe

Flamingo Tongue Snail

This snail is not commonly encountered in the hobby, for good reason. However, it’s often showcased in scuba-diving photos, which means hobbyists get excited. Unfortunately, it’s a corallivore in cowry family, Ovulidae. Although its spots make it attractive, they are only a part of its mantle.

Margarita Snail: Not [Typically] Responsibly Reef Safe

Margarita marine snail

Last (and least), we have the Margarita (or Margarite) snail. Sadly, these snails are typically taken from colder water, given a tropical-sounding name, and sold as tropical species. They slowly cook internally over a few weeks to months then perish. Please do the responsible thing and discourage import of these colder water species by not purchasing them (unless you have a coldwater tank). If you do purchase these, they may have a better chance of survival in a cooler tank (e.g., 72-78 degrees F).

There are much better choices, especially the captive-reproducing species. Supposedly there are warmer-locale species, and they survive quite well in reef tanks. However, it appears they are rarely imported nowadays (as they’re typically only found in deep waters), and the coldwater species are more common. This is probably the most tragic reason why identification of marine snails is crucial: to only collect suitable and sustainable inhabitants.

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