Snails in the Aquarium

Just like any other force, snails can be used for good and for evil. They have a reputation of rapidly devouring plants, multiplying like crazy and turning a former fish tank into an unsightly mass of creeping grey slime, but this is only the dark side of the snails. When properly managed, snails can actually do a lot of good in your aquarium. If you introduce factors that balance their numbers, they will settle in to their designated ecological niche in your aquarium and carry out the same beneficial work that they do in the wild. Snails can even be entertaining pets themselves and some of them, e.g. the Mystery Snail, look really beautiful.

Advantages of snails in the aquarium

Snails and water quality
The exact diet of a snail depends on size and species, but a majority of the snails are scavengers that will feed on plants (especially decomposing plants), algae and dead animals. Some of them are carnivores that will hunt, but only tiny animals such as gastropods smaller than themselves. An animal that will remove dead animals, algae and decomposing plants from your aquarium sounds like a nice deal, doesn’t it? A reasonable amount of snails will actually help you to keep the water quality up in the aquarium while simultaneously keeping algae growth in check. Snails are highly dedicated cleaners that will get into a lot of nooks and crannies where catfish wouldn’t bother. 

Snails and fish eggs
Keeping the water quality up in a breeding aquarium is often of extreme importance and introducing a scavenger will help you with this. The problem with scavenging fish species is however that many of them like to eat fish eggs. Even fish species that normally stick to an herbivore diet can be tempted by the look of tasty fish eggs. Snails are however much less fond of eating healthy fish eggs and are therefore a good choice of scavenger in a breeding aquarium.

Will they eat my plants?
Yes, snails do eat plants, but most species actually leave healthy plants alone and prefer to feed on dead and decaying plant matter that would only end up fouling your water anyway. Healthy plants tend to produce cyanides and other poisons and are therefore not appreciated by most snails. There is however exceptions to this rule, e.g. the Pond snail, which should never be introduced to the aquarium since they can rapidly devour even healthy plants. The myth that snails destroys plants probably originates from their habit of settling on dying plants and rapidly multiplying there due to the abundance of food offered by a plant that is already dying. Snails also like to graze on algae growing on plant leaves and this can naturally look as if they are munching away at the plant itself, when they are in fact only ridding the plant of algae.   

Controlling snails in the aquarium

Even though snails can be a good addition to most aquariums, their numbers must be kept in check. There are also certain species, including the abovementioned Pond snail, that need to be eradicated completely if you keep a planted aquarium. Snails are especially prone to multiply rapidly in hard alkaline water and the aquarist must therefore pay special attention to their numbers in such aquariums. Snails need the minerals to form their shells and too soft and acidic conditions can actually cause the shell to dissolve and leave the snail completely unprotected from predators.

Decreasing the food supply
If you experience a snake bloom in your aquarium you might be over-feeding your fish, because left over food is an excellent food source for snails. Watch your fish carefully at feeding time. Is there any food left after 3-4 minutes? Then you are most likely over-feeding your fish and need to decrease their servings. Uneaten food should also be removed from the aquarium after each feeding session if you want to keep the snail population at bay.

Introducing predators
One of the reasons why snails can multiply like crazy in an aquarium is of course that they lack natural predators. In the wild, the amount of snails is constantly kept in check by various snail-eating species in their normal habitat. In every biotope where you can find snails, you can also find animals that have turned into skilled snail-hunters. In Asia, you can for instance encounter the beautiful Clown Loach (Botia macracanthus). Introduce a group of Clown Loaches in your snail infested aquarium and watch them as they skillfully grab the unprotected soft part of the snail and suck the entire animal out of its protective shell. In the ocean, the Pufferfish has developed a completely different tactic and will use its strong jaws to crush the shell of the snail before devouring the soft parts.  

The lettuce method
Run hot water over a lettuce leaf and place it on the bottom of the aquarium just before you turn the lights out. You may have to tie something to the leaf to prevent it from floating, or jam it under a stone. Before you turn on the lights in the morning, pick up the lettuce leaf and all the snails that cover it. You need to repeat this every night until the snail population is under control. If you want to speed up the process, use several lettuce leaves each night.

Chemicals
Fish stores normally sell various brands of snail killing chemicals, but these should only be used as a last retort. Compounds potent enough to kill snails normally wreck havoc with the populations of beneficial bacteria as well and can cause great disturbances that turn a fairly balanced aquarium into a highly unstable environment.

Keeping snails out of the aquarium

If you do not want to introduce any snails to your aquarium, you should soak plants and gravel in warm salty water before use. 10 minutes in salty warm water will kill the snails and can also prevent other organisms from entering your aquarium, e.g. the Ich parasites that causes White Spot Disease. Remember to thoroughly wash away the salt afterwards.

Basic snail info

Snails belong to the phylum Mollusca, a phylum where you will also find clams and oysters. All members of this phylum have soft bodies without any skeleton or exoskeleton, and have therefore developed other ways of protecting and stabilizing themselves. The members of the class Gastropoda, the class to which all snails belong, have for instance developed a single shell into which they can withdraw. 

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