Snails: why are they so essential?

In natural aquaristics, where the balance of the aquarium is the top priority, it is unimaginable to do without snails, whether in an aquarium or in an outdoor pond.

But why?

Of course, we are all happy to see a new species arrive in our little ecosystem, and each new snail is already a pleasure in itself. We have an aquarium, it is true, primarily for the joy of contemplating a small aquatic world with its inhabitants that evolve there.

But the reason why these snails are essential lies elsewhere.

"As I have often explained, the biological cycle of a fish-populated aquarium is broken, it is not complete."

And this has a very simple explanation: there are many more fish in aquariums than in nature.

In a natural pond, each fish has, on average, between one and ten cubic meters of water (i.e., 1,000 to 10,000 liters) to itself. It is with this very low density that the aquatic ecosystem functions normally. Microfauna is abundant, and fish are at the top of the food chain. An insect that lays eggs in a pond has a good chance that some of its offspring will survive the fish and manage to fly away one day.

In an aquarium, no.

The fish density there is a thousand times higher!

"Let’s just say that, with the fish swimming in circles all day in such a small volume, no appetizing creature stands a chance of escaping them."

"It's exactly the same as giving a hen one hectare of meadow or just 10 square meters all year round. There's little chance that a single blade of grass or a worm will remain in the second case."

The aquatic biological cycle, which requires the presence of a large and varied micro-fauna, is therefore disrupted in an aquarium and thus incomplete.

Fish eat anything that tastes bad for being alive and bigger than a bacterium!

The function of this microfauna, which is largely "detritivorous", is therefore not guaranteed.

And its function is precisely to reduce organic waste into particles that can then be attacked by microbes. In the absence of these little creatures, bacteria find themselves alone in having to degrade organic elements that are too large and complex without assistance.

For example, in nature, green water is a blessing: it doesn't"ourrit the daphnia, which then feed the fish that, coincidentally, reproduce at the same time."

In an aquarium, green water becomes a problem precisely because the slightest daphnia will be gobbled up before it can start its work. And the water will become increasingly green, until the microscopic algae that make it up die en masse, severely polluting the water. Hence the principle of the ZollaBox Clear Water, which allows the daphnia to work.

The same goes for fish carcasses: ostracods that should consume them are banned from staying, too quickly devoured. Only the water lice, a bit larger and more resilient, manage to settle if the fish are not too big.

"That is why snails are so valuable. They are part of those detritivores, but they are the only ones that can keep fish at bay thanks to their shell."

THE In the presence of the very rare fish that eat them, snails can work and lead their lives peacefully without being devoured. And they are practically the only detritivores capable of doing so.

"It is therefore almost solely thanks to the snails that an aquarium with fish can regain a complete biological cycle."

Personally, I turn my back on tropical, exotic snails, which we don't know what to do with if we stop fishkeeping and which sometimes colonize natural spaces if we release them there. This was the case with ampullaries, highly valued by aquarists and now banned for this reason.

The only exception I make to this principle is the malaysian Trumpet Snail (above). Because they do not survive the winter in our latitudes and therefore do not risk being invasive. And above all, they are the only ones that bury themselves for a good part of the day, thus ensuring a micro-aeration function of the soil that plants appreciate.

Otherwise, the ramshorn snails have become a classic in the aquarium, with their different color varieties.

But their tiny cousin, the planorbids, is practically unknown. Fascinating and discreet, it is a true curiosity of nature.

The bladder snail, small, fun (it sometimes swims on its back!) and plant-friendly. Unlike its cousin the great pond snail, which sometimes nibbles on them when it runs out of algae to eat. The two complement each other wonderfully in the pond, the great pond snail loving to come out of the water to nap on a leaf of floating frogbit or on an iris!

In a "creature" aquarium, with or without shrimp but without fish, the micro-fauna can live safely. All species form an incessant ballet and provide a display of the natural cycle.

But the snails, less irreplaceable in this case, remain visible and aesthetic actors of great value, adding their species to the biodiversity of the whole.