Care guide · Freshwater snails

Great ramshorn snail

Planorbarius corneus

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The great ramshorn snail (Planorbarius corneus) is a large, flat-coiled freshwater snail from Europe and nearby parts of Asia. The aquarium trade uses “ramshorn snail” for other species too, including Planorbella duryi, so a shop label alone is not a certain identification. This species is better suited to a temperate, often unheated aquarium than to a permanently hot tropical tank. It grazes algae and biofilm and consumes detritus and leftovers, but does not replace maintenance. Habitat and food supply matter more than an arbitrary minimum tank size. Pay particular attention to shell condition, overfeeding and the possibility of young snails.

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At a glance

Temperature: 12–25 °C
pH: 6.5–8.0
Diet: Omnivore, detritivore
Adult size: Up to 4 cm
Temperament: Peaceful

About this species

Planorbarius corneus (Linnaeus, 1758) belongs to the family Planorbidae. WoRMS/MolluscaBase and GBIF treat the older combination Planorbis corneus as a synonym or former name. Aquarium sources report a flattened shell up to about 4 cm across; specimens around 2.5 cm are more usual. “Ramshorn snail” is not a unique trade name. Check the scientific label and do not automatically confuse this large European species with the smaller Planorbella duryi.

Natural habitat

The species inhabits plant-rich still or slow-flowing freshwater. Sources describe shallow margins with aquatic plants, algae, periphyton and decomposing plant matter. The snail can reach the surface to take in air; physiological research describes the role of its lung cavity and haemoglobin in oxygen uptake. This does not make poor water quality safe. Keep an unobstructed route to the surface and never release aquarium animals, eggs, plants or water into natural waters.

Aquarium and layout

Choose a mature freshwater aquarium with bottom and grazing area, firm surfaces for biofilm, and shelter among plants or hardscape. The snail travels over glass, leaves, substrate and décor and must be able to reach the surface. Specialist minimum recommendations range from 20 to 50 litres, so this guide does not state a universal minimum. Consider a shell width up to about 4 cm, food supply, tankmates and population management. A stable temperate aquarium is a better fit than one kept continuously at high tropical temperatures.

Water conditions

The aquarium profiles reviewed overlap around 12–25 °C: Aquarium Glaser gives 12–25 °C and Wirbellosen-Aquarium 10–25 °C. Their pH ranges differ; their shared range is about 6.5–8.0. These are care recommendations, not an experimental optimum. Avoid prolonged heat, abrupt swings and very soft, mineral-poor water. One source warns that lime-poor water can damage the shell. Sources do not establish a consistent universal GH/KH threshold, so do not add minerals blindly. Ammonia and nitrite should not be detectable.

Behaviour and group size

The great ramshorn snail does not form a school. It grazes on biofilm, thin algae, detritus and leftover food. A visit to the surface to breathe air is normal and does not by itself indicate distress. Abundant food can accelerate reproduction and increase the population. The species is usually described as peaceful, but it is vulnerable to larger crayfish and animals that actively eat snails; its shell has no closing operculum. Assess actual tankmates rather than relying only on overlapping water values.

Feeding

The diet includes algal growth, biofilm, decaying plant matter, detritus and leftovers. Aquarium sources say healthy plants are usually spared, while other species references also list living aquatic plants. A manufacturer FAQ warns that soft young shoots may be nibbled during acute food shortage. Avoid both starvation and chronic overfeeding: offer small portions and remove leftovers. No central-catalogue product has been individually confirmed for this snail based on reliable composition and use data, so this guide links no branded product.

Breeding

Planorbarius corneus is a simultaneous hermaphrodite that lays gelatinous egg masses on firm surfaces. Aquarium and biology sources describe flat or oval clutches; size and hatching depend on conditions. A laboratory study examined reproduction during long-term culture, but its results do not predict the number of young in a home aquarium. With suitable food, a small group may produce more snails. Check glass, leaves and décor for egg masses. Consider population growth before purchase and never release animals or eggs outdoors.

Keeping with fish

No controlled trial covers this snail with every aquarium fish. Small, peaceful fish can only be considered where temperature and mineral conditions suit both species. Predatory fish or fish that pick up snails are not a safe choice. The related-species section therefore lists the neon tetra only as conditional, mainly because the water-profile overlap is limited; it does not assume attacks on adult fish.

Keeping with other invertebrates

This species is itself a freshwater invertebrate snail and is generally described as peaceful. That does not make every pairing with shrimp, crayfish or other molluscs automatically safe. Larger crayfish and specialized snail-eaters can attack it; no controlled trial was found for every specific snail pairing. Consider relative size, food competition and water minerals. Do not add a species merely because general pH values overlap.

Exoskeleton, shell and minerals

This snail does not moult like a shrimp; its shell grows with the animal and is extended at the margin. Adequate minerals therefore matter, but the sources reviewed do not establish a universal GH or KH target for every aquarium. Use reliable measurements and avoid abrupt corrections. A damaged or eroding shell can have several causes and is not a diagnosis by itself. Access to the surface and appropriate food remain part of basic care.

Possible problems

Do not confuse this large great ramshorn with every small snail sold or found under the common name. The trade name is used for several species with different adult sizes and temperature preferences. Other problems include prolonged heat, very soft water, insufficient food and uncontrolled reproduction caused by overfeeding. Larger crayfish and specialized snail-eaters are a risk. Buy with a dependable species label, observe shell and behaviour, and keep surplus animals and aquarium water out of the wild.

Sources & review

This care guide draws on several specialist sources and was last checked on 17 October 2026.

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