Snails in an aquarium: friends or foes?
Should we adopt snails and which ones to choose?
Snails are rarely absent from our aquariums, poubellariums, or ponds.
Either because they were deliberately introduced, or because they arrived as stowaways clinging to a plant, or even on the leg of a bird that brings you a bit of the mud from the neighboring pond!
In almost all cases, the introduction of these snails, whether intentional or not, is followed by the rapid emergence of a strong population.
This demonstrates both the prolificacy of these animals and, above all, their usefulness in our small ecosystems.
Indeed, if they settle so easily, it is because they occupy an empty space. This is what is called a vacant "ecological niche."
Our fish feed on all the microfauna that normally does the work of waste degradation. It is therefore generally no longer there to fulfill this function, and the snails, protected by their shell, are then infinitely valuable for getting rid of waste.
Snails are therefore doubly essential, as they are often the only micro-fauna that fish tolerate without devouring it!
'Without them, the biological cycle cannot be completed, and a dead fish that has not been removed will have to decompose entirely due to bacteria, and thus too slowly, polluting the entire environment significantly.'
In fish-populated ponds, this is also true, even if a bit of micro-fauna sometimes manages to escape their appetite and is therefore not completely nonexistent.
But, overall, snails are one of the only solutions to ensure biological cycles in an ecosystem where fish are more numerous than in nature, which is the case in all our aquariums, poubellariums, and ponds.
Let's remember that, in nature, there isn't even one fish for 10,000 liters!
To a certain extent, snails also eat algae. Generally, however, they will only be able to limit its growth, but their omnipresence at all times on plants, glass, and other surfaces keeps the algae in check. As for the plants, some species will nibble more than others. Others will not touch them at all, feeding exclusively on dead tissue and never on living parts.
Regarding maintenance conditions, they only fear excessively soft and acidic water, which can in some cases be aggressive to their shell. Exotic species must be kept indoors in winter, which is not the case for others that can spend the winter in ponds in our regions.
Small inventory:
The ramshorn snail (Planorbarius corneus)
This snail is of respectable size once adult, reaching up to 15 mm in diameter, and even more exceptionally. Its brown spiral shell is flat and it can come in different colors such as blue or pink, depending on the distribution of melanin on its body and/or shell. The color is genetic and hereditary.
The ramshorn snail breathes in the air because it has a lung. It periodically rises to the surface to breathe, which is why it is able to survive in waters that are very low in oxygen.
Its maintenance is more than easy: the water parameters are indifferent, and it also tolerates soft and acidic water. The ramshorn snail can perfectly spend the winter in an outdoor pond, where it will live slowly on the bottom, where the temperature remains less freezing.
"She is very prolific, laying her eggs on walls, supports, windows, and plants. They are quite flat translucent masses. Each individual is both male and female, but must meet a second one to mate. The two individuals can then lay eggs together."
The population becomes numerous if the waste is abundant, for example if you overfeed your fish. Their number is then what saves the aquarium from pollution. But if the aquarium is very clean and resources start to run low, the adults will eat the smaller ones that have hatched, and the population will thus regulate itself.
The ramshorn snail is essentially a detritivorous vegetarian and only munches on plants in cases of severe scarcity. Because it normally only eats dead tissue or algae.
The bladder snail (Stenophysa marmorata)
The Bladder snail is a very small snail, measuring almost always less than one centimeter. It is very common in all aquatic ecosystems. Its small size makes it quite discreet in an aquarium.
"It is neither difficult for the water temperature nor for the temperature, spending the winter outside without difficulty. It compensates for its small size with its number. Indeed, it constantly lays eggs sheltered in a transparent gelatinous mass."
Like the ramshorn snail, it breathes in the air and often comes back to the surface.
"It is often seen swimming on its back just below the surface: this behavior is actually for it to consume the bacterial film that forms on the surface. This makes it absolutely essential in natural aquariums where the water moves little at the surface."
She is a detritivorous vegetarian and therefore hardly eats plants, feeding on dead parts and especially algae.
Its reproduction is quite unique in the animal world as it is capable of parthenogenesis. A single snail can then, without having to mate, give birth to other individuals! Otherwise, like the ramshorn snail, each individual carries both sexes and mates with another so that both can lay eggs.
The melanoid (Melanoides tuberculata)
"It's the famous 'pointed' snail from our aquariums!"
Tropical in origin, the melanoid will not survive the winter outdoors.
It is a snail that is bound to the substrate, which will not be able to reproduce if it cannot burrow into the soil, whether it is earth or sand. It spends a good part of the day there, coming out a little more often at night. Its movement is slow, and it drops to the bottom at the slightest contact. Its tireless work as a burrower allows it to mix the substrate with infinite slowness and gentleness, eliminating pockets of fermentation and bringing various elements to the roots of the plants.
Water that is too soft or acidic can damage the tip of its shell.
The melanoid has no need to breathe at the surface: it breathes underwater with gills, like fish.
This snail eats ONLY garbage, and ALL the garbage!
Like the bladder snail, it can reproduce by parthenogenesis, that is to say, alone and without any mating. This ability is reserved for females only, as this snail has separate sexes, unlike the ramshorn snail and the bladder snail. Males are therefore disadvantaged and, in fact, quite few in number.
When the malaysian Trumpet Snail retreat into their shell, a lid closes like a door. They are therefore very well protected and practically invulnerable to fish.
The great Great pond snail (Lymnaea stagnalis)
This very large snail (up to 5-6 cm!) is somewhat unique in aquaristics.
The great Great pond snail is stunning, with its long and pointed silhouette and its dark brown dress.
She does not go unnoticed!
It is an indigenous snail that can easily spend the winter outdoors. In an aquarium, it should be kept away from tanks that are too heated, exceeding 25 or 26°C.
Equipped with a lung, it breathes at the surface. It is not uncommon to see it taking air out of the pond, resting on a floating branch or an emerged leaf.
Not very discreet, it is easy to see her swimming, both in an aquarium and in a pond. Her backstroke, when she eats the bacterial film on the surface, is quite irresistible!
Individuals carry both sexes, mate in pairs, and then lay abundantly. The large Great pond snail is therefore very prolific.
"It may be the most voracious snail for algae, but it is also criticized for attacking plants. This is largely true: every medal has its reverse. This voracity is highly appreciated in ponds where both algae and plants can quickly become invasive…"
"His Achilles' heel is that, unlike the melanoid, nature did not give him an operculum when he retreats into his shell. This, in the face of certain very persistent carnivorous fish, can in some cases make him prey."
Mattier, July 9, 2023
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