Snails in the aquarium.
Aquarists often wonder: what are snails in an aquarium — a blessing or a curse? One thing is certain — they have no place in a spawning tank with caviar. For hungry snails, very few types of food are as much of a delicacy as fresh fish eggs. And if snails were to satisfy their hunger by eating just a few eggs entirely, no, apparently their greatest pleasure is destroying the membranes of every egg they can reach. However, putting snails into an aquarium with sufficiently grown fry is not only possible, but also beneficial. Sometimes it is difficult for an aquarist to determine how much food growing fry need. Undernourishing fry leads to severe growth retardation. Excess food, on the other hand, leads to its decay and the death of most of the fry.
All snails kept in aquariums affect the biosystem in one way or another. In most cases, they are still beneficial. Snails are not only capable of doing very useful work in the aquarium, but they actually do it. With snails successfully dealing with excess food, the danger of overfeeding fish is significantly minimized. The beneficial activity of mollusks lies in the fact that they eat leftover food that has fallen to the bottom and not picked up by fish, destroy rotting plant debris, and thus carry out part of the general metabolic cycle in the aquarium. By eating excrement, food scraps, and plant remnants, mollusks convert them into a state more accessible for further processing by bacteria.
When feeding with Tubifex or bloodworms, they often watch for food to appear right under the strainer or at the spot where live food is lowered. Snails suck food out of the substrate. In aquariums where soft water is required, they bring benefit by converting calcium into an insoluble state. They do not damage plants as long as they have enough food — algae growth. But if there is a shortage, they switch to eating plant leaves. In addition, they eat dead fish and thus ensure that toxic substances do not accumulate in the aquarium. Physa snails eat the bacterial film on the water surface.
You should not take mollusks directly from natural bodies of water, as many of them serve as intermediate hosts for various parasitic animals that can cause various fish diseases. Mollusks imported from tropical waters have adapted to life in an aquarium, so the probability of fish contracting any diseases is very low. Under no circumstances should you keep various pond snails and viviparous snails taken from local waters in aquariums, as they are often carriers of various fish diseases. Pond snails feed on plants and release mucus into the water, polluting it. Our local snails have a rather strong mouth apparatus and will graze on plants even with hard leaves.
Bladder snails and *Physa* are completely undesirable guests in planted aquariums — they do a good job of removing algae and coatings, but at the same time they do not spare aquatic plants at all, eating small holes in the leaves. In an aquarium where *Physa* are kept, all plants have deformed, punctured leaves. It is also impractical to introduce exotic tiger snails into aquariums, as they feed on underwater plants. Bivalve mollusks such as *Anodonta* and *Unio* are completely inappropriate in an aquarium with other fish, as they breathe oxygen dissolved in the water, competing in this with our pets. And most importantly, the larvae of these mollusks, hatching from eggs, attach to the bodies of fish using sticky filaments, embed themselves in their skin, encyst in it, and essentially parasitize them for 2–3 months.
In a cold-water aquarium (up to 20°C), you can keep domestic species of mollusks bred in captivity, since those taken from natural waters can carry fish disease pathogens. In a tropical aquarium, Brazilian ramshorn snails (*Marisa cornuarietis*), *Melanoides tuberculata*, and *Pomacea* are kept. The number of mollusks should not be too large; while they do eat leftover food and destroy certain types of algae, they consume oxygen, reducing its content in the water, enrich the water and substrate with excrement, and a number of species, when hungry, will turn to plants.
Completely undesirable aquarium residents include: red ramshorn, red *Physella*, gray *Physa*, river snail (*Viviparus*), *Pomacea*, *Anodonta*, horn ramshorn, great pond snail (*Lymnaea stagnalis*), and bivalve mollusks like freshwater mussels. Burrowing snails bring benefits to the aquarium—tropical *Melanoides*, which constantly live in the substrate where they finish off leftover food. By burrowing through the substrate, they ensure good gas exchange, preventing the decay of organic matter. With them, the biological balance is more stable. Aquarium snails can be bought at an aquasalon, pet store, or market from advanced aquarists.
Snails that have lived in captivity for a long time are not demanding about water quality. Among the advantages of snails is that they are hardy and adapt perfectly to any conditions, able to survive a certain number of “critical days” in the aquarium. They can live both in clean, running, oxygen-saturated water and in water cluttered with rotting organic debris. In addition, snails are a good indicator of oxygen levels in the water. If the water is low in oxygen, snails often rise to the surface to gulp fresh air. In general, you can use the same water quality criteria for fish regarding ammonia, nitrites, nitrates, etc. Except that the pH is preferably maintained between 7 and 8.
Most snails prefer hard water rich in calcium salts. If the water is too soft, they cannot build a good shell, and the shell will be sensitive to damage. However, even in good conditions, some individuals have minor defects, especially in the old part of the shell. If only the surface is damaged, you have nothing to worry about. Wild-caught snails may be more picky about water quality. Optimal water temperature ranges from 18 to 28°C. Like many cold-blooded animals, they are more active at elevated temperatures, eating, crawling, and growing faster. Also, higher temperatures stimulate reproduction. At 18°C, they become numb, hibernate, or become very sluggish. With a further drop in temperature, they begin to die.
Common food for snails consists of dead plant parts and what the fish didn’t eat in time — leftovers of dry or live food that settled to the bottom. And in this regard, they are certainly useful. Combating algae overgrowth on aquarium walls and plant leaves with the help of mollusks is ineffective, because they will only cover the glass with a pattern of eaten patches. Snails eat filamentous algae and algae growing on the aquarium glass. However, they cannot cope with such quantities, and the aquarium walls will not be clean thanks to them. If the aquarium is not cleaned for a long time, you can see the snail’s trail where it grazed on the algae. The notion that mollusks eat and process fish excrement is mistaken.
In aquariums with ornamental tropical fish, *Physa*, ramshorns (*Planorbidae*), *Melanoides*, and *Pomacea* are the most widespread. Ramshorns and *Physa* are the easiest to keep. In an aquarium with favorable conditions, they very quickly begin to lay eggs. Small transparent clutches can be found on plants, glass, and stones. Fully formed baby snails hatch from the eggs, only very small. In natural conditions, *Melanoides* inhabit freshwaters from Egypt to India. Most of the time they spend burrowed in the substrate.
Coarse sand (particle size 2–3 mm) is best suited for *Melanoides* in an aquarium. Mollusks cannot burrow into a substrate made of stones that are too large. *Melanoides* loosen the sand well and prevent it from souring. At the same time, they do not damage plant roots. They lay eggs on the underside of stones. The downside is that these snails reproduce quickly, and controlling their numbers is very difficult.
The most interesting aquarium mollusks are *Pomacea* (apple snails). They came to us from the tropics of South America. Apple snails are very similar to the well-known river snail, but much larger (up to 5 cm). Coloration depends on age. Young individuals have a dark brown, almost black color. As they grow, they lighten, and yellowish stripes appear on the shell. The brightest coloration is observed when the snail reaches a size of 2.5–3 cm. Even sturdy plants can break under their weight.
Bivalve mollusks breathe with gills and, unlike snails, are sluggish. They act as living biological filters, absorbing turbidity and microscopic organisms along with water. However, it should be borne in mind that most bivalve mollusks from domestic waters cannot live in water whose temperature exceeds 20°C.
Be sure to cover the aquarium with *Pomacea* with a glass lid, otherwise don’t be surprised to find a snail on the floor in the morning. Don’t worry, they can survive without water for more than a week, but there is a danger of shell damage during a fall. It is very important to have enough free space above the water (at least the size of the shell) so that the snail can crawl out of the water to lay eggs. Alas, people often forget about this.
The most difficult thing is to protect them from fish, especially the young ones. After all, newly hatched snails can be eaten even by guppies. And bettas, macropods, loaches (*Botia*), *Dario*, *Badis*, large swordtails, barbs, cichlids, especially if hungry, deal with adult ramshorns and *Physa* as well. Fish wait for the snail to poke out of its “fortress,” grab it by the soft body, and sharply shake the prey. As a result of this operation, an empty shell falls to the bottom. Large cichlids and puffers take the mollusk into their mouths entirely, chew it, and spit out the shell fragments.
Snail leeches in the aquarium. With beautiful imported Sulawesi mollusks, mainly *Tylomelania*, leeches that harm snails began to be introduced into aquariums. Sometimes leeches were also found in plants ordered from online stores. Small leeches that hunt ramshorns and pond snails also live in Russian waters. There are cases of them being introduced into the aquarium with local plants or substrate. When buying new snails, as well as plants, it is necessary to quarantine the “newcomers” in a separate container for at least two weeks. If the snails become inactive in quarantine, hide in their shells a lot, or you notice strange spots on their bodies, you need to check them for leeches and carry out treatment.
Snail leeches are called *Clepsine* or *Glossiphonia*. Flat, brownish in color, with numerous speckles on the body, they attach to the snail’s body using a sucker. They feed using a proboscis, sucking small snails out of their shells and drinking blood from larger ones. When in danger, leeches curl up into a ball. Each leech produces from one to several dozen babies, so if you don’t start eradicating them in time, the aquarium can turn into a breeding ground for leeches.
You can try to remove leeches mechanically, manually with tweezers, but this is very laborious. Moreover, the problem is that many leeches hide under the snail’s shell. Therefore, it is necessary to force them to come out. How to do this? Experiments have proven the effectiveness (though not 100%) of salt baths for snails. 1 teaspoon of salt is taken for 400 ml of water. Snails are placed in such a bath for 10 minutes, as a result of which leeches leave their “houses”, and the snails return to the quarantine tank or are transferred to the general aquarium without “passengers”. Such procedures can be done once a week. True, *Tylomelania* themselves do not like salt. But here you have to choose the lesser of two evils.
By the way, all remedies used to combat snail leeches are also dangerous for snails. Therefore, during the treatment process, you may lose a certain percentage of mollusks. But there is no other way to get rid of this trouble.
The product “No Planaria” helps kill leeches both in the quarantine tank and in the general aquarium. Snails also feel unwell from it, but it is better to eradicate all leeches by losing a few snails than to lose all snails by feeding them to leeches. When leeches are found, every effort must be made to get rid of them as soon as possible, even if it means losing some snails.
It often happens that even with a large amount of eggs, the population of mollusks does not increase, and sometimes becomes smaller and smaller. In this case, it is best to move a dozen snails to a small aquarium or jar and feed them abundantly, changing the water frequently. There they will multiply rapidly, and you can constantly add them to your main aquarium. Ramshorns, *Physa*, and young other mollusks cannot be kept with cichlids. *Melanoides* are in relative safety, as they spend almost all their time in the substrate. As for apple snails (*Pomacea*), even the largest aquarium fish have a hard time dealing with their sturdy shells.
Many species of snails reproduce faster than the fish and plant owner would like. The presence of a large number of snails is an indicator of an unhealthy aquarium. For snails to live, they must not only find enough food, but also consume oxygen and produce organic waste. Some of them devour fish eggs. The population must be kept within reasonable limits. The number of mollusks should not be too large, because while they do eat leftover food and destroy certain types of algae, they consume oxygen, reducing its content in the water, enrich the water and substrate with excrement, and a number of species, when hungry, turn to plants. If you know the volume of the aquarium, you can calculate how many snails are needed from the ratio of 1 large snail per 8–10 liters of water.
Sometimes it happens that all the snails suddenly die. The cause of this is most often the snail leech, which is introduced into the aquarium along with live food. Getting rid of it is very simple: it is enough to remove all snails, and it will die of hunger. After that, the mollusks are reintroduced into the aquarium.
