The bladder snail: a true algae eater

1 – How do you recognize the bladder snail?

Formerly Physa marmorata, its new name is Stenophysa marmorata.

The bladder snail is a very pretty little aquatic snail whose size does not exceed 1 cm. Only a few very rare "giant" individuals exceed this size. To differentiate the bladder snail from its cousin the great pond snail, you need to look at its shell from the back: if you see it coil in a clockwise direction to the tip, then it is a bladder snail. The great pond snail coils in the opposite direction.

As it grows, the bladder snail is also distinguished by the appearance of spots or mottling in all shades of brown, hence its scientific name.

The bladder snail is "pulmonate", meaning it breathes at the surface and not underwater like fish, and does not have a shielded operculum to protect itself when it retreats into its shell, unlike the melanoid.

 

2 – What does the bladder snail eat?

The bladder snail is primarily an algivore. The basis of its diet, since it hatched from the egg, consists of algae. Besides algae, it only eats decomposing tissues (dead plants or animal remains), and even bacteria. This is what makes it fun: its irresistible way of swimming on its back at the surface actually allows it to feed on the film of bacteria and algae (the "biofilm") that forms on the surface of water bodies.

For the bladder snail to attack a healthy plant, it really needs to find nothing else. This is what makes it so popular in aquariums as well as in ponds, since it limits its diet to algae and dead or sick tissues!

 

 

3 – How does the bladder snail reproduce?

Like many snails, the bladder snail is hermaphroditic: it has both sexes. It can therefore mate with any other individual, each fertilizing the other's eggs!

But she also has the option, if she does not find a partner for a long time, to resort to parthenogenesis: she then produces offspring without mating. This means that a single individual, in an aquarium, will eventually, after a long wait, reproduce and thus populate the space.

The bladder snail is even the first animal in the world in which "castrator" genes have been identified that can, in certain individuals, sterilize their male part and thus turn them into pure females.

The eggs of the bladder snail are enclosed in a transparent "gel" attached to any support. Over the days, the white embryos appear, then hatch. They only turn brown later, and eat algae right from hatching.

 

 

4 – How to host it?

In a pond, the bladder snail lives without making a fuss and even spends the winter without any difficulty. Its population naturally adapts to the available algae. Its small size allows it to reach all the nooks and crannies, but also occasionally serves as a meal for a large fish or an amphibian.

The bladder snail being, in the natural environment, hosts to certain parasites and pathogens that can affect fish, it is not advisable to introduce individuals from your pond into the aquarium.

Aquazolla raises bladder snails without contact with fish for several generations to avoid this risk.

In an aquarium, it will not experience winter and will live at the same pace all year round. It will eat algae, but also any carcass or food waste that may have escaped you. It thus becomes the health insurance of the aquarium.

"Do not feed her specifically, or she would then lose that virtue."

Also think about not leaving it in an aquarium where the surface is very close to the edge. Indeed, it has, like the great pond snail, the habit of coming out of the water from time to time, and could then escape, with no hope of survival.

Finally, the bladder snail is one of the few snails that can tolerate very soft water, even acidic water, although it obviously prefers water that is richer in minerals for its shell.

 

5 – Does the bladder snail pollute the aquarium?

"If you do not feed it, it will not pollute the aquarium at all: indeed, it only recycles elements already present in the aquarium, contributing to the recycling cycle of various waste. Its droppings contain only nitrogen and phosphorus that it has drawn from the algae and not from outside the aquarium! And the aquarist will generally prefer a snail's droppings, which will nourish its plants, rather than an algae!"

The bladder snail is therefore a strict "detritivore", constantly recycling elements already present in the ecosystem, without ever bringing any from the outside.

 

6 – How to limit its population?

The bladder snail is small. This is what makes it charming, but it complicates and makes its capture laborious if it becomes too numerous.

First of all, remember that its population increases when algae and food waste increase. It is only a symptom, and even the remedy!

If you limit external inputs (especially fish food), it will therefore be less omnipresent.

The introduction of glossiphonies (harmless small leeches) can limit their number, as they will target the smaller ones. But this remains a very moderate predation, and some glossiphonies may sometimes, for lack of better options, prey on the Blackworms, or even shrimp and the aselles.

 

But, in a natural aquarium, these cycles of moderate predation among various critters are also somewhat what is sought after, aren't they?