Lymnaea stagnalis

The Great Pond Snail is one of the largest freshwater snails you can keep in an aquarium and is very easy to care for, making it great for beginners. It's a highly active creature that you'll see exploring all parts of your tank, from the gravel to the glass, and even up to the water's surface to take a gulp of air. This snail is an excellent cleaner, constantly munching on algae, leftover fish food, and decaying plant matter. However, be aware that its big appetite extends to healthy aquarium plants, so it's not the best choice for a carefully planted tank.

They are not picky about their water conditions and can live happily in a small, unheated tank. These snails reproduce very easily by laying clear, jelly-like egg sacs on plants and tank surfaces. While this can be interesting to watch, their numbers can increase very quickly, so you might need to manage their population. They are also known for being escape artists, so a tight-fitting lid on your aquarium is a must. Overall, they are fascinating, hardworking snails, but their plant-eating habits and rapid breeding mean you should think carefully before adding them to your community.

The Great Pond Snail, Lymnaea stagnalis, is a notable invertebrate in the freshwater aquarium hobby due to its impressive size and robust nature. Originating from temperate regions across the Northern Hemisphere, it is highly adaptable to a wide range of aquarium conditions, making it a suitable choice for novice aquarists. Its ability to thrive in cooler water means it does not require a heater and is comfortable in typical room-temperature setups. While it can tolerate warmer, tropical temperatures, this often accelerates its metabolism, leading to a faster growth rate but a potentially shorter lifespan.

As an omnivorous detritivore, its diet is incredibly varied. In an aquarium, it serves as a relentless scavenger, consuming biofilm from all surfaces, clearing algae, and finishing any uneaten fish food that settles on the substrate. This cleaning ability helps maintain water quality. However, its voracious appetite is a double-edged sword. Lymnaea stagnalis is a known plant-eater and will readily consume soft-leaved aquatic plants like Cabomba or Elodea, making it unsuitable for delicate aquascapes. To supplement its diet and deter it from devouring prized plants, offer blanched vegetables such as zucchini, spinach, or kale, along with commercial foods like algae wafers and pellets. A good diet rich in calcium is essential for healthy shell development.

Behaviorally, this snail is constantly active. One of its most interesting traits is being a surface breather. It possesses a primitive lung, allowing it to utilize atmospheric oxygen. You will frequently observe it gliding up to the water's surface to replenish its air supply, an adaptation for life in low-oxygen, slow-moving ponds. This also contributes to its reputation as a tank escape artist, and a secure lid is non-negotiable to prevent it from crawling out. Although socially solitary and content on its own, it is a prolific breeder. As a hermaphrodite, any two snails can reproduce, laying transparent, gelatinous egg clutches on tank glass, decorations, and plants. These can hatch within weeks, and without intervention or natural predators (like loaches or pufferfish), a pair of snails can quickly lead to a significant population, increasing the overall bioload on the aquarium's filtration system.

Lymnaea stagnalis, a member of the class Gastropoda and family Lymnaeidae, is a large, pulmonate freshwater snail with a Holarctic distribution. Its morphology is characterized by a thin, dextrally coiled (right-handed) shell that is conical and elongated with a pointed apex. This species serves as a significant model organism in fields such as neurobiology, developmental biology, and ecotoxicology due to its large, identifiable neurons and simple, easily-tracked reproductive cycle.

Physiologically, L. stagnalis is highly adaptable. It is eurythermal, capable of tolerating a broad temperature range, though its metabolic processes, growth, and reproduction are temperature-dependent. Its respiratory system is a key adaptation; as a pulmonate snail, it possesses a vascularized mantle cavity functioning as a physical gill-lung. This allows for aerial respiration, where the snail periodically comes to the water's surface to exchange gas. This behavior is crucial for survival in lentic, potentially hypoxic environments, supplementing its cutaneous respiration. The species exhibits robust osmoregulatory capacity, allowing it to inhabit waters with a wide variance in pH and mineral content, as indicated by its tolerance for a total dissolved solids level up to 300 ppm and a broad hardness range.

Ecologically, it functions as a primary consumer and detritivore. Its feeding behavior involves grazing on periphyton, biofilm, and, notably, macrophytes, which can alter the primary producer community structure within an ecosystem. Its omnivorous diet contributes to a medium waste output and a bioload factor of 2.8 in closed aquatic systems, impacting nutrient cycling. Reproduction is prolific; the species is a simultaneous hermaphrodite, with cross-fertilization being the predominant strategy. Gelatinous egg masses are deposited on submerged surfaces, and development is direct, without a free-swimming larval stage. This high fecundity and ease of breeding contribute to its occasional status as a pest species in managed aquaria. Its widespread distribution and resilient population dynamics are reflected in its IUCN status of 'Least Concern' (LC).