Snails in the aquarium: friends or foes?

Should you adopt snails and which ones should you choose?

 

 

Snails are rarely absent from our aquariums, trash tanks, or ponds.

Either because they were intentionally introduced, or because they arrived as stowaways clinging to a plant, or even on the leg of a bird that brings you some mud from the neighboring pond!

 

In almost all cases, the introduction of these snails, whether intentional or not, is followed by the rapid appearance of a strong population.

This demonstrates both the prolific nature 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 called a vacant "ecological niche."

 

Our fish feed on all the microfauna that normally does the job of breaking down waste. It is therefore generally no longer there to fulfill this function, and snails, protected by their shells, are then infinitely precious for making waste disappear.

 

Snails are therefore doubly indispensable, as they are often the only microfauna that fish tolerate without devouring!

 

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 heavily.

 

In ponds populated with fish, this is also true, even if some microfauna sometimes manages to escape their appetite and is therefore not completely absent.

 

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 for all our aquariums, trash tanks, and ponds.
Remember that, in nature, there isn’t even one fish per 10,000 liters!

 

To some extent, snails also eat algae. Generally, however, they can only limit its growth, but their omnipresence at all times on plants, glass, and other surfaces keeps algae in check. As for plants, some species will nibble on them more than others. Others will not touch them at all, feeding exclusively on dead tissues 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 15 mm in diameter, or 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 on the shell. The color is genetic and hereditary.
The ramshorn snail breathes air because it has a lung. It therefore periodically comes up to breathe at the surface, which is why it can survive in waters very poor in oxygen.

Its maintenance is more than easy: water parameters do not matter, and it also tolerates fresh 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.
It is very prolific, laying its eggs on walls, supports, glass, and plants. These are fairly flat translucent clusters. Each individual is both male and female, but must meet a second one to mate. The two individuals can then lay eggs.

The population becomes numerous if 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 out, the adults will eat the smaller ones hatched from the eggs, and the population will regulate itself.

The ramshorn snail is essentially a vegetarian detritivore and only nibbles on plants in cases of severe shortage. Because it normally only eats dead tissues or algae.

 

 

The bladder snail (Stenophysa marmorata)

The Bladder snail is a very small snail, almost always measuring less than one centimeter. It is very common in all aquatic ecosystems. Its small size makes it rather discreet in aquariums.

It is not picky about water temperature or air temperature, spending the winter outside without difficulty. It compensates for its small size by its number. Indeed, it constantly lays eggs sheltered in a transparent gelatinous mass.

Like the ramshorn snail, it breathes air and therefore often returns to the surface.

It is often seen swimming on its back just below the surface: this behavior actually consists of consuming the bacterial film that forms on the surface. This makes it absolutely indispensable in natural aquariums where the water moves little at the surface.

It is a vegetarian detritivore and therefore hardly eats plants, feeding on dead parts and especially algae.

Its reproduction is quite unique in the animal world since it is capable of parthenogenesis. A single snail can then, without mating, 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 malaysian Trumpet Snail (Melanoides tuberculata)

It is the famous "pointed" snail of our aquariums!

Of tropical origin, the malaysian Trumpet Snail will not survive winter outdoors.

It is a substrate-bound snail that cannot reproduce if it cannot bury itself in the soil, whether it is earth or sand. It actually spends a good part of the day there, coming out a bit more often at night. Its movement is slow and it lets itself fall to the bottom at the slightest contact. Its tireless digging work allows it to stir the substrate with infinite slowness and gentleness, eliminating fermentation pockets and bringing various elements to the roots of plants.

Water that is too soft or acidic can attack the tip of its shell.

The malaysian Trumpet Snail has no need to breathe at the surface: it breathes underwater with gills, like fish.

This snail eats ONLY debris, and ALL the debris!

Like the Bladder snail, it can reproduce by parthenogenesis, that is, 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.

When malaysian Trumpet Snails retract into their shells, an operculum closes like a door. They are therefore very well protected and practically invulnerable to fish.

 

 

The Great pond snail (Lymnaea stagnalis)

This very large snail (up to 5-6 cm!) is somewhat unique in aquaristics.

The Great pond snail is superb, with its long and pointed silhouette and dark brown shell.

It does not go unnoticed!

It is a native snail, which can easily survive winter outdoors. In aquariums, it is best to avoid tanks that are too warm, exceeding 25 or 26°C.

Equipped with a lung, it breathes at the surface. It is not uncommon to see it take air outside the pond, resting on a floating branch or an emerged leaf.

Not discreet, it is easy to see it wandering, both in aquariums and ponds. Its swimming on its back, when it eats the bacterial film on the surface, is quite irresistible!

The individuals carry both sexes, mate in pairs, then lay eggs abundantly. The Great pond snail is therefore very prolific.

It may be the most voracious algae eater, but it is also criticized for attacking plants. This is largely true: every coin has its flip side. This voracity is highly appreciated in ponds where both algae and plants quickly become invasive…

Its Achilles' heel is that, unlike the malaysian Trumpet Snail, nature did not give it an operculum when it retracts into its shell. This, when faced with some very persistent carnivorous fish, can in some cases make it prey.

 

Mattier, July 9, 2023