Tropical Brackish Water Snails

Snails are often added to the aquarium for algae control and as scavengers. In the case of pufferfish, they might also be used as live food. Some snails are highly beneficial, others less so; it is important to choose and use snails carefully.

Snails (non-nerites)

Snails are popular with aquarists because they tend to be hardy, easy to keep and generally harmless towards other livestock (except soft plants and fish eggs). Most freshwater snails, such as apple snails, are not salt-tolerant and have no place in the brackish water aquarium.

Melanoides tuberculata is known among biologists as the red-rimmed melania, but aquarists usually refer to this small freshwater snail as the Malayan livebearing snail or Malaysian trumpet snail (often abbreviated to MTS). Though not large (typically around 3 cm/1.2") these snails are certainly attractive in their way, with a sturdy, spire-shaped shell bearing a delicate pattern of spiral grooves. Adult snails are usually marked with reddish-purple bands and spots, particularly on the final whorl of the shell. The closely related quilted melania Tarebia granifera is sometimes mistaken for the Malayan livebearing snail. Its much more globular rather than spire-shaped shell and the absence of colour banding easily distinguishes it from the Malayan livebearing snail. It does not naturally occur in brackish water and has minimal tolerance for brackish water in the aquarium. Another similar species is the fawn melania Melanoides turricula that has the same tall shell as the Malayan livebearing snails but lacks the red markings. Again, this species isn’t a resident of brackish water and is more normally found in clean, fast-flowing streams.

Malayan livebearing snails are essentially hardy animals that pose no problems to the aquarist in terms of maintenance. They will accept a very wide range of water conditions, from slightly soft and acidic through to fairly strong brackish water (at least SG 1.012). Water temperature does not matter greatly, and they will accept anything from 18˚C to over 30˚C. One of the more remarkable aspects of the biology of these snails is their ability to enter a period of dormancy is conditions become hostile. In the wild they will hibernate through cold periods and aestivate through droughts, sealing the aperture off to prevent moisture loss. There are many reports of Malayan livebearing snails surviving in buckets of gravel or sand for months at a time, only to spring back into life as soon as that gravel is put into a new aquarium.

Curiously for such attractive and easily maintained snails, opinion is sharply divided as to whether these snails are a blessing or a curse. To their credit, these snails never touch live plants. They burrow through the substrate keeping it oxygenated and clean, eating any organic matter they can find. They are especially good at preventing organic matter from decaying anaerobically in sandy substrates. On the debit side of the equation is the fact that these snails can breed very quickly if there is plenty for them to eat. So while plagues of these snails really say more about poor aquarium maintenance than anything else, they do have a reputation for being a pest.

Pachymelania byronensis is a West Africa snail that is periodically sold for use in freshwater aquaria. These are impressive snails, having shells that get to about 6 cm/2.5" in length and are covered in short but sturdy spines. In the wild this species inhabits the upper part of estuaries where it can be found in either freshwater or brackish water to a salinity below about one-quarter that of seawater (in aquarium terms, 1.000 to 1.005). At least two other species of Pachymelania are known, and these are found further down the estuary in saltier water. All Pachymelania are believed to have planktonic marine larvae, so breeding these snails in aquaria is likely to be difficult, perhaps impossible. These snails appear to be more omnivorous than herbivorous, and they ignore plants and eat little algae. On the other hand, fish foods of all types are readily accepted.

One final thing should be mentioned about the Pachymelania snails: they are known to carry parasites transmissible to humans. As such, they should be quarantined and treated before being introduced to your aquarium. Check with your retailer whether this has been done before buying them, and if in doubt, consult with your medical practitioner. Nerites and ampullariids are not known to carry dangerous parasites, and in fact ampullariids are used to exterminate such species of snails by eating their eggs and out-competing them for food, so these can be used safely in any aquarium. Wild melanias, including the Malayan livebearing snail, have been reported to carry parasites, but because these parasites need to pass through a variety of hosts such as fish and birds that eat the snails, to complete their life cycle, aquarium populations pose no risk at all.

A more problematic addition to the brackish water aquarium is the Colombian ramshorn snail, Marisa cornuarietis. Despite its common name, this snail is in fact a member of the apple snail family Ampullariidae. Most ampullariids are rather intolerant of salt, but Marisa cornuarietis is an exception and naturally occurs in both fresh and brackish water environments. In an aquarium it can be expected to do well at a salinity of up to about one-quarter strength seawater (SG 1.005) though rather less would be preferable. As such, it could make a useful and geographically authentic addition to a low-end brackish water aquarium containing Central American livebearers or killifish such as mollies and Florida flagfish.

Snails (nerites)

Nerite snails feed almost exclusively on algae, predominantly diatoms and green algae, but in the case of the American zebra nerite at least, blue-green algae as well. Most species are found in saltwater habitats, but many live in tidal areas including brackish water habitats, and a few are exclusively freshwater residents. Nerite snails are perhaps the ideal algae-eating animals for the brackish water aquarium, with the only caution being that some fish, notably puffers, will view them as food. Nerites tend to be quite small, typically no more than 15 mm in shell width, so you should allow at least 2-3 per 45 litres/10 gallons if you want them to use them for algae control. Nerites do not breed in freshwater tanks since most species have a saltwater larval stage, but even in brackish water tanks it is very unlikely nerite snails will succesfully breed, though many species quite happily lay their eggs on solid surfaces.

Various freshwater nerites have become commonly traded in recent years, and most should do well at low salinities (SG 1.005 or less). These include the polka-dot or orange-track nerite Vittina semiconica; the African zebra nerite Neritina natalensis; and the Indo-Pacific zebra nerite Vittina coromandeliana. The freshwater limpet Septaria porcellana is another nerite snail, and can be expected to adapt to low salinity systems below SG 1.005.

Some nominally freshwater nerites are known to inhabit areas with tidal or brackish water influence, and should adapt to a broad range of brackish water salinities up to around half-strength seawater (around SG 1.010). These include the spiny nerites such as Clithon corona and Clithon sowerbyana, and Batman snail Neripteron auriculata.

Other nerites are primarily marine species that may occur in brackish or freshwater habitats periodically. These will do best at middling to high salinities, SG 1.010-1.025, even if sold as freshwater nerites, as sometimes happens. Examples include the Virginia nerite Neritina virginea, the American zebra nerite Puperita pupa, and the Indo-Pacific chameleon nerite Nerita chamaeleon.