Freshwater Snail Species In The Hobby

(Thread rework in progress - please pardon our dust!)

Freshwater Snail Species In The Hobby​

(Two Clea helena assassin snails and a Planorbid ramshorn - photo by CassCats)

Index

• Basic Terminology for Identification
• Physidae: Bladder Snails and Tadpole Snails
• Lymnaeidae: Pond Snails
• Planorbidae: Ramshorn Snails
• Acroloxidae: Freshwater Limpets
• Viviparidae: Trapdoor Snails and Live-Bearing Mystery Snails
• Ampulariidae: Apple Snails and Mystery Snails
• Cerithoidea: Thiaridae and Pachychilidae: Trumpet Snails and Rabbit Snails
• Neritidae: Nerite Snails
• Clea (Anentome) helena: Assassin Snails
• Potamopyrgus & Bithynia: Mud Snails and Faucet Snails

Basic Terminology for Identification

Anatomy:

• Foot: the bottom, muscular portion of the animal used for locomotion.
• Siphon: a proboscis-like appendage appearing on the side of the shell in some species.
• Mantle: the soft tissue inside the opening of the shell.
• Spire: the conical part of a snail's shell ending in a point.
• Aperture: the opening of the shell housing the snail's body.
• Operculum: the plate that covers the aperture on some species when the animal retracts. The operculum is a horny, sometimes calcareous plate that attaches to the back of the snail's foot.
• Whorl: a “level” of the spire or full revolution of the shell.
• Suture: the boundary between whorls.

Shell shapes:

• Dextral shell: when holding the shell so that the spire points up and the aperture is towards you, the aperture is on the RIGHT side of the shell.
• Sinistral shell: when holding the shell so that the spire points up and the aperture is towards you, the aperture is on the LEFT side of the shell.
• Planispiral shell: a disk-shaped shell (ramshorn shape). Planispiral shells can still be dextral or sinistral, but the spire is not visible when viewing the shell head-on.
• Globose shell: a very rounded shell that is closer to being sphere-shaped.

Physidae: Bladder and Tadpole Snails
Other common names: “pest” snails, pond snails (shared with Lynmaeidae)


(Physa acuta, photo by connorlindeman)


(Shell of Physa acuta from wikipedia, the most common freshwater aquarim "pest" snail. Note that the opening is on the left, sinistral, when the spire is up and the opening is facing forward).

Description
Physids are a large group sinistral snails. They are omnivores and will consume microalgae as well as uneaten fish foods and decaying plant and animal material. Most species are fairly small, reaching sizes of no more than 1cm. The shell is thin and clear (and rather fragile as a result), with any coloration being due to the snail's mantle showing through or covering the shell in some species. The mantle of many species has a dotted or mottled appearance. There is no operculum.

Physids are simultaneous hermaphrodites, but prefer to mate to reproduce. Self-fertilization is possible, but not as common as reports in the hobby might suggest. In fact, the majority of aquarium cases of a single snail laying fertilized eggs are probably due to the snail having mated some time before being introduced. Physids can mate at a fairly small size and store sperm for some length of time. A single mating can result in many fertilized clutches spread out over as much as a few months. Eggs clusters are enclosed in a mass of jelly about 4-5mm long.

Care
Physids can be so easy to care for that population control or eradication become a bigger concern for many hobbyists. Although some of the rarer Physid species are more fragile and require attention to the conditions found in their native habitat, the commonly seen species like Physa acuta are virtually bomb-proof, being able to tolerate almost any conditions suitable for fish tanks and ponds. Some Physids can create thriving populations in tropical tanks as well as temperate ponds that freeze over for months in the winter. Parameters like pH and KH are largely irrelevant to caring for these species, as the shells of many Physids are more corneous than calcarious. The shells are often quite thin and fragile.

Physids tend to arrive in aquariums by accident, usually on live plants, and then survive on uneaten food and other decaying debris in the tank. For tanks that are over-fed, one Physid carrying fertilized eggs can quickly create an army of snails. Care should be taken when trying to manage Physid populations via starvation alone, as they will sometimes respond aggressively towards slow-moving tankmates out of desperation. Large populations of Physids have been known to swarm and kill other snails. Species lacking operculums are especially vulnerable to this starvation-induced behavior, although even large Ampullariids can become targets.

Lymnaeidae: Pond Snails



(Shell of Lymnaea stagnalis from wikipedia. Note that the opening is on the right, dextral, when the spire is up and the opening is facing forward)


Description
Lymnaeids are often confused with Physids due to the similar appearance. Despite similarities in size, color, and shell shape, Lymnaeids are easily distinguished by the fact that their shells are dextral. Shell shape ranges from quite conical and long (such as in some Lymnaea species) to very globose with a very large aperature to spire size ratio (such as in Radix) and there is no operculum. Lymnaeids have the same general diets as Physids and the same type of reproduction strategy.

Exact species identification within the family is often quite difficult, although two species sometimes seen in aquariums and also native to areas in Europe are more easily identified and perhaps the most well-known members of the family: the “giant pond snail,” Lymnaea stagnalis, and the “big-eared Radix,” Radix auricularia. Both of these snails reach relatively large sizes for the family, with L. stangnalis sometimes reaching lengths of 6cm (although such large individuals are somewhat exceptional) and R. auricularia growing up to 2-3cm in length. Although Lymnaeids are generally species, R. auricularia is more aggressive and will actively prey on smaller snail species. Lymnaeids appear in the aquarium trade primarily in areas with color climates (such as Canada and areas of the UK) while being almost totally unseen in others (such as the southern USA).

Care
The most well-known Lymnaeids like L. stagnalis and R. auricularia are coldwater snails. Many other Lymnaeids also come from temperate regions where the water temperatures rarely reach into even the lower end of the tropical temperature range used for many home aquariums. Even prolonged temperatures of 21-22C/70-72F are too high for long-term survival of species from cold regions, and individuals placed under those conditions usually die in only a few weeks. As a result, many Lymnaeids species are best suited for coldwater aquaria or, in their native ranges, outdoor ponds. When at a suitable temperature, Lymnaeids are similar to Physids, being tolerant of a fairly wide range of pH and KH values, although they will benefit from a pH of 7.0 or higher and a correspondingly higher KH. Warmer water Lymnaeid species do occur sometimes in the aquarium trade but are fairly rare.

Planorbidae: Ramshorn Snails
(Note that this common name is also shared with Marisa cornuarietes in Ampulariidae)



(Red Planorbid, photo from wikipedia)

Description
Planorbids are the second most commonly seen group of accidentally introduced snails in the aquarium trade next to Physids, often showing up as hitchhikers on live plants. With few exceptions, Planorbids have planispiral shells and are usually brown (small species may be clear), sometimes with a mottled appearance. There is no operculum. Unlike other hitchhiker families, some Planorbids can exhibit an impressive range of colors with selective breeding. The wild coloration is a dark brown, but red individuals show up fairly commonly. Red individuals are actually albinistic, as the snails have haemoglobin in their blood (red when oxygenated, blue when not), while most snails have haemocyanin (blue when oxygenated, clear when not). When the albinism also affects the shell, the snail appears solid bright red with the red body showing through the clear shell. Additionally, striking yellow and even bluish varieties of at least one species have been produced by breeders.

Planorbids have the same reproduction strategy as Physids, and self-fertilization is again fairly rare. Egg cases are leathery and round. Since Planorbids' populations are usually easier to control by limiting food access than is the case for Physids, they are an appealing “cleanup” animal for many aquariums and can also be quite visually interesting when the recessive color traits show up. Planorbids can also be employed in limiting Physid populations as a competing species.

Exact species identification is generally quite difficult, as with Physids and Lymnaeids. Species commonly seen in the trade belong to four main genera: Planorbis, Planorbella, Helisoma, and Gyraulus. Species belonging to Planorbella and Planorbis are commonly seen in Europe. In North America, Helisoma anceps is widespread (usually differentiated by V-like appearance of the sides of the aperature and deep, angular sutures), but Planorbella species also occur. Gyraulus species are usually small and clear, sometimes no more than a few millimeters in diameter.

Care
Most Planorbids seen as accidental arrivals in the trade can thrive in a wide range of environmental conditions, similarly to Physids. However, they will benefit from a higher KH and pH. While they can survive in very soft, acidic water, the shells often become eroded and irregular-looking. Severly eroded shells may also shorten the lifespan of the adult snails even if it does not have a serious impact on the population as a whole. This can be avoided with a pH of >=7.0 and at least a mild KH reading (such as 4dKH). Most species commonly seen as accidental inclusions in the trade will thrive in standard tropical aquarium temperatures. Species from coldwater environments will not last long at those temperatures, but they are relatively uncommon in the trade.

Planorbis corneus is one of the more famous members of the genus: the “great” or “giant” ramshorn from Europe. They grow quite large, up to 5cm across and are sometimes confused with Marisa cornuarietis due to their size and common name. Unfortunately for many snail enthusiasts, the great ranshorm is a coldwater species and does not thrive at tropical temperatures, suffering similar problems to the Lymnaeids from the same regions. Some other, smaller coldwater species can suffer similar problems. P. corneus appears somewhat frequently in Europe for use in temperate ponds. Various warmer-water species in both Planorbis and other genera are often misidentified as Planorbis corneus in the trade.

Acroloxidae: Freshwater Limpets


(photo by Alexander Mrkvicka on wikipedia)

From https://www.fishforums.net/threads/snail-species.75554/ :
"They are both really small snails and their hood-shaped and limpet like shells don't have whorls. They aren't really limpets, but they resemble them (...). They breathe through skin and lung. They don't fill their lung with air like most of the other pulmonate snails, but they keep it filled with water. The walls of the lung sack have lots of blood vessels, that makes it easy to exchange oxygen and carbon dioxide through the walls. When the snail has used up the oxygen from the water (or air) and it is filled with carbon dioxide, the snail will release the old water and take in new.

They usually won't do much damage to plants since they are really small, but they can look really ugly if there's too many of them. If you look closely, through magnifying class, you might find these little hermaphroditic (snail has both sexes, but usually need other snails to fertilize the eggs) snails interesting.”

Viviparidae: Trapdoor Snails and Live-Bearing Mystery Snails
(Note that some members of Amulariidae are also referred to as "mystery snails")

Cipangopaludina chinensis:


Description
Viviparids are a group of snails that give birth to fully-formed young snails instead of laying eggs. They have dextral shells, an operculum, and trunk-like snouts. In many species, males are easily distinguished by having uneven-length feelers, with one being specialized for mating purposes. Species like Viviparus malleatus, Cipangopaludina chinensis, and C. japonica are commonly seen in the trade. These species are also invasive in some parts of North America.

Care
Viviparids are able to tolerate a fairly wide range of water parameters. However, although they may be found in quite acidic water in the wild, these conditions in an aquarium can still lead to shell erosion over time. A pH over 7.0 and access to calcium-rich foods will help avoid this. Both C. chinensis nor C. japonica tend to fare poorly at the consistently high temperatures seen in tropical aquariums – it results in a short lifespan and decreased maximum size. These species are best kept in unheated aquariums (provided the room temperature is not too high) or outdoor ponds in temperate regions.

Viviparids will eat decaying matter and soft film algaes. Although they are not a risk for eating live aquarium plants, large individuals have the potential to uproot plants when digging in the substrate. The Viviparids commonly seen in the trade grow too large to survive by scavenging alone in most aquariums and require some sort of supplemental feeding, which must be in the form of sinking food that also turns soft. Fresh vegetables are not advisable even though they can attract Viviparids. Because of the way their mouths are structured, the snails will have difficulty doing anything but “licking” the surface of vegetables until they start to rot, which can rapidly foul the water. Foods like sinking algae wafers that turn into a soft mush as they absorb water are more easily consumed.

Ampulariidae: Apple Snail and Mystery Snails
Other common names: one species of this family, Marisa cornuarietis, is also called the giant ramshorn snail.

NOTE: many countries now have laws restricting possession of Ampulariids – check your local laws to determine whether keeping these snails is legal.

Pomacea diffusa:


Pomacea insularum:


Pomacea canaliculata (photo by TwoTankAmin):


Two completely different kinds of ramshorns: three Marisa cornuarietis (giant ramshorns) with smaller Planorbids:


Description
Ampulariids represent one of the more popular groups of ornamental snails. They have a siphon that is used to breath, transferring air to and form a lung within the shell.

Species documented in the trade include:

• Pomacea. diffusa (formerly known as P. bridgesii): the most commonly seen species of apple or mystery snail. Shells have right-angled sutures and are usually no more than 2” in length, and in individuals with colored shells there is a white stripe following the sutures. A diverse array of colors of this species have been produced through selective breeding, including yellow, white, and purple varieties. Eggs are laid above the waterline and are pale pink and irregular in shape, being closely fused with neighboring eggs in the clutch. Unlike the other species described below, P. diffusa generally do not harm live plants if well fed.
  
  
• Pomacea. canaliculata: the channeled apple snail. Although frequently sold under the same common name as P. diffusa and also having several common color varieties to add to the confusion, these snails are differentiated based on their deep, channel-like sutures and eggs that are sphirical and more loosely packed. P. canaliculata can be very difficult to distinguish from P. insularum except by egg diameter and maximum size.
  
  
• Pomacea insularum: the largest species seen in the trade, P. insularum frequently reaches 3” in size and sometimes 4”. Although the suture shape is somewhat different in most cases than for P. canaliculata, correct identification of smaller individuals is still difficult except to a very trained eye. Egg clutches are distinguished by having many more and much smaller diameter eggs than for P. canaliculata.
  
  
• Pomacea haustrum: rarely seen in the trade, these snails grow to a moderate size (2-3” in captivity) and lay green eggs above the waterline.
  
  
• Pomacea. paludosa: the Florida apple snail. These snails grow up to 3” in diameter, having globose shells with fairly smooth sutures (although this varies). Eggs are large and white, laid in clusters above the waterline. There has been relatively little success raising P. paludosa in captivity, and individuals hatched in captivity rarely survive to adulthood.
  
  
• Asolene spixi: these are a small species of apple snail, rarely reaching more than 1” in size. They have yellow and brown banded shells, although some degree of color variation has been observed in captivity. Eggs are laid in gelatinous masses underwater.
  
  
• Marisa cornuarietis: the only planispiral apple snail, these snails are very similar in appearance to Asolene spixi in terms of coloration. Eggs are laid in gelatinous masses underwater.

Care
These snails must have access to air above the waterline. Tanks where the waterline is flush with an upper pane of glass can actually drown these snails over time. Some species have short siphons and therefore need space to have their shell partially above the waterline to breath. Many species also lay their eggs above the waterline, making falling out a risk for females kept in open-topped tanks with a high waterline. To accommodate both breathing for all species and egg-laying in species with aerial eggs, 2”/5cm of space above the waterline and a lid is recommended for Ampulariid tanks. Large snails may require as much as 4”/10cm or more to accommodate egg-laying behavior.

Apple snails require hard water with a reasonably high pH to avoid shell erosion. A pH of 7.4-7.8 and a KH of at least 6 are good targets to aim for. Apple snails are NOT tank janitors suitable for algae removal. Although they will eat algae, they have mouth parts suitable for eating a much wider variety of foods and are omnivores that should have access to both protein- and calcium-rich foods in addition to algae and/or other vegetable matter*. Apple snails are also incredibly messy animals, easily as messy if not more-so than many commonly kept fish.

Apple snails should not be kept with nippy fish or those with more predatory tendencies. Fish like bettas will often rip off the long feelers and eat them (although the feelers grow back, they are likely to just be eaten again), which can cause the snails to be stressed and hide for much of the day and/or have difficulty feeding.

* Be cautious with fresh vegetables! Vegetables that can be peeled before feeding (like cucumber) are safest for use as foods in an aquarium. Some pesticides used on food meant for human consumption can affect snails (and sometimes fish) within minutes of exposure. Unfortunately, these chemicals are not always removed by simply washing the vegetables, particularly if the chemicals have ended up under a wax coating.

Cerithoidea (Thiaridae & Pachychilidae): Trumpet and Rabbit Snails
Other common names: Malaysian trumpet snails (MTS), Sulawesi snails


(Melanoides tuberculata photo from wikipedia)

Thiarids are a group of freshwater snails where most species reproduce by parthenogenesis, a form of asexual reproduction. Therefore, only a single individual from most species is required to produce a colony in an aquarium. Similarly to Viviparids, eggs develop inside the mother and offspring are released as fully formed little snails. Thiarids are also remarkably hardy, being able to withstand adverse water conditions by burrowing into the substrate and closing up. Most thiard species seen in the trade do not exceed 1”/2.5cm in length. Tarebia granifera and Melanoides tuberculata are two of the more commonly seen species.

From https://www.fishforums.net/threads/snail-species.75554/ :
“Shell is conical, 5 -> spires, they have [an] operculum, heart shaped mouth and thin tentacles. Malaysian trumpet snails, MTS, are really useful snails. They eat algae and leftover fish food (also dead fish and fish eggs), dead plant material and they will usually leave live plants alone. They burrow in the sand during daytime unless there are too many snails or the substrate is too compacted and going bad. They will help with keeping the sand loose. When the lights are off the snails head towards the surface and start eating algae.”

Species known as rabbit or Sulawesi snails from Pachychilus and Tylomelania sometimes appear in the aquarium trade, although they are a fairly rare and recent addition. These freshwater snails are similar to Thiarids in terms of overall appearance and behavior, although some Pachychilid species seen in the trade are larger and with brightly colored bodies.

Neritidae: Nerite Snails
Note that common names for this group have become complex and sometimes seller-specific relating to the color of the shell.

Neritina sp. photo from Essjay. See the bottom of this post for additional photos of this highly variable group of snails.

Description
Nerites are fairly small snails with very thick, globose shells. The family contains species that range from freshwater to marine environments (note: the marine species should NEVER be acclimated to lower salinities). Nerites seen in the freshwater aquarium trade belong to three genera: Neritina, Theodoxus, and Clithon. The most commonly seen species for sale are:

• Neritina reclivata (olive Nerite)
• Neritina virginea (virgin Nerite)
• Neritina natalensis (zebra Nerite)
• Theodoxus fluviatilis (river Nerite)
• Clithon corona (horned or spiny Nerite)

With few exceptions, the “freshwater” Nerites sold in the aquarium trade are not completely freshwater. Some are brackish but tolerate freshwater, others are found in freshwater to brackish regions and tolerance for freshwater may vary with collection location. Species found in freshwater, again with few exceptions, cannot reproduce in freshwater. There is some evidence of various Theodoxus species being able to reproduce in full freshwater (there is at least one Theodoxus species that has been found in totally isolated freshwater environments), but success cases are still relatively uncommon.

Nerites have separate genders and lay small, calcareous, white eggs ~1-2mm in size on hard surfaces. Part of the difficulty involved in breeding many Nerite species is that the offspring generally do not hatch out as small snails, but rather go through a larval stage more common of marine species called a veliger. This stage is free-swimming, incredibly small, and incredibly difficult to feed. In some species that normally hatch as veligers, egg cases have also been observed to rarely hatch in captivity as a small snail instead, but the reason for the difference is unclear. A downside of Nerites is that, even though most sold in the trade cannot produce surviving offspring in freshwater, if a male and female are present, they will still attempt to be prolific. Some hobbyists find the abundance of little white specs on everything to be an eyesore.

Care
Nerites can be kept in tropical tanks and will eat film algaes and uneaten fish food. They generally will not eat hairy algaes. The water for Nerites should be hard, with a fairly high pH to avoid shell erosion. A pH of around 7.8 and >6dKH is a good target. In more acidic or soft conditions, the shells are very prone to pitting and rapid erosion. Fortunately, Nerites are pretty good at repairing these damaged areas when environmental conditions improve, so patching is rarely a concern for badly-eroded shells.

Nerites that come from a wide range of salinities in the wild may be problematic in a freshwater aquarium. N. reclivata is perhaps the most problematic in this regard. Hobbyists with Nerites from brackish regions often remark that the snails do not spend much time in the water or regularly escape the tank even when there is a lot of space between the waterline and the rim of the tank. In fact, this is a big warning sign that the snails are unhappy in their environment, and the behavior can be stopped by adjusting the salinity (usually increasing it, since the behavior is generally in response to full freshwater). When the conditions aren't changed, the snails usually don't survive very long and tend to die within a few weeks to months. Nerites that are content in their environmental conditions will live for years and can even be kept in open-topped tanks, provided that there is at least some space between the waterline and the tank rim to make sure the snails don't fall out by accident when looking for food. Occasionally crawling a small distance out of the water for a short period of time is normal behavior, but spending most of the time out of the water or trying to escape the tank on a daily basis is a sign of stress.

Other Photos of Nerites

Examples of Neritina natalensis, from Essjay. Common names for this species include Zebra Nerite and Red Onion Nerite.


Examples of Neritina sp. from Essjay. These are likely color variations of either Neritina virginea (Virgin Nerite) or Neritina reclivata (Olive Nerite).


Clithon sp. from Essjay. Most species of Clithon have spines of varying lengths, although this one does not.


Theodoxus fluviatalis photo by Michael Manas on wikipedia.


Neritina sp. by Gamegurl564

Clea (Anentome) helena: Assassin Snails


(image from wikipedia)

Clea helena is species of freshwater whelk within Buccinidae. The vast majority of other species in the family are saltwater, with some species being common additions to marine aquariums. It is important to note that C. helena's freshwater nature is quite unusual in the family; the marine species that are plentiful in the trade should NEVER be acclimated to lower salinities.

Buccinid whelks have a long siphon, which is used to “smell” the water and potential food items. These snails will generally bury themselves for long periods of time and leave this siphon extended above the substrate to smell for feeding opportunities.

Buccinid whelks are carnivores, and some actively hunt other Mollusks. In addition to the siphon, these whelks also have a long proboscis that is normally kept retracted within the head area, only being extended through the mustache-like mouth during feeding. The proboscis on Buccinid whelks is quite long and flexible, allowing them to bypass the defenses of many Bivalves and snails, sneaking in through small openings where the shell does not close tightly together to chew on soft tissue. Most Buccinids, including Clea helena, will also feed on other animals and meaty foods when they have the opportunity, although they are only likely to successfully prey on animals that are either quite slow-moving or injured/incapacitated such that they cannot flee the snail's advances.

As with other Buccinid whelks, C. helena has separate sexes. Breeding can take place in an aquarium, but usually with low survival rates of the offspring.

Potamopyrgus & Bithynia: Mud Snails
Other common names: faucet snails, New Zealand mud snail (Potamopyrgus antipodarum specifically)

Bithynia from CassCats


Mud snails are tiny species, some of which resemble a Viviparid - but at a fraction of the scale, typicaly no more than a few millimeers long up to 1cm for some species. Mud snails can be distinguished from actual Viviparids by the fact that they have extended spirals despite their tiny size, while young Vivipairds of the same size actually have a much more globose appearance and don't develop the same elongate shape until they are much larger. Although appearing quite similar in shell and body shape, and falling under the same common name umbrella of "mud snails," species in the genera Potamopyrgus and Bithinia are taxonomically quite removed from one another. One particularly prolific species of mud snail, the New Zealand mud snail (Potamopyrgus antipodarum) has become invasive in a number of regions in North America, Europe, and Asia.