Imagine the scene; You’ve just managed to get your new aquarium the way you like it, and are admiring it in all it’s glory, when out of the corner of your eye, you spot a snail gliding slowly over the glass. How do you react? Maybe you're horror-struck, imagining it attacking your fish or devouring your plants. Or perhaps you’re just shocked and wondering how the snail managed to find its way into your tank in the first place.
This article will attempt to answer some of the questions you may have about snails and lay any fears to rest.
Snails belong to the Gastropoda genus of the phylum Mollusca. The members of the Mollusca phylum don’t possess a skeleton or exoskeleton and include clams, oysters and squid, as well as snails and slugs.
So, how did the snail get into the tank?
The most common way for snails to enter your aquarium is by hitching a ride on live plants. Even if you haven’t bought or added new plants in a while, chances are, the snails have been there all the time, hiding in the gravel or behind décor, and let’s face it, you didn’t set up an entire aquarium for snails alone, so you weren’t exactly looking out for them.
Will they harm the fish?
If you're a beginner to the fishkeeping hobby and don’t know much about the different forms of aquatic life it’s easy to worry when first spotting an intruder in the aquarium, and obviously the first thing you think of is whether or not they’re going to attack or harm the fish, but most freshwater snails are harmless to fish, quite happily living alongside them and filling a niche in the aquarium that fish sometimes don’t. If anything, the fish are more likely to be a threat to the snails than the reverse, as some species of fish will predate on snails.
In general, the biggest risk that snails represent to fish is by introducing parasites into the tank, which may later migrate to the fish.
When kept in moderation, snails can be beneficial to the fishkeeper. Many of them are scavengers, and will eat algae and detritus, which helps to keep the whole aquarium that little bit cleaner (not that anyone is suggesting you let the snails do all the maintenance work for you – that’s still your responsibility) and for some species, such as the Malaysian Trumpet Snail, their habit of burrowing in the substrate for food keeps the substrate turning over and stops it from becoming compacted, which reduces the risk of a build-up of hydrogen sulphate – a fish toxin if allowed to build up and escape into the water.
Some species are even intentionally bought and added to the tank by the fishkeeper themselves, either for one of the reasons mentioned above, or simply because they can be an interesting, colourful and sometimes even beautiful addition to the tank.
Snails and Plants
If snails eat algae, do they also eat plants?
That depends on the species of snail. While some snails will feast on healthy plants and ruin the look of your otherwise perfect aquarium, many don’t bother plants unless the plant is dying anyway.
Here’s a quick guide to some of the more common species of freshwater snail.
A popular addition to aquariums as a desired pet, rather than an unwanted intruder, the Apple Snail is divided into at least 4 different genera – not all of which are plant-safe. A widespread family of snails, with species found from S. America to Asia, there are roughly 120 different species of Apple Snail.
Diet: Depends on the species. Some, such as Pomacae Bridgesii (the one most likely to be bought from the pet shop) are scavengers, which will leave live, healthy plants alone in favour of detritus or algae. Others will take all vegetation.
Maximum size: between 2 and 6”, depending on species.
Malaysian Trumpet Snails (or MTS) have cone-shaped shells and are known for their habit of burrowing in the substrate, which helps to keep it loose (particularly sand) as they search for any leftover fish food. They tend to come out at night, after the aquarium lights are switched off.
Diet: Detritus and algae
Maximum size: 2cm
Considered a pest by many fishkeepers, Ramshorn snails are small snails that reach about 1”. They can be black or red in colour. They are plant-safe unless the plant is dying, preferring detritus and algae to healthy live plants, however, they’re hermaphrodite so any 2 Ramshorns can breed. They breathe air from the atmosphere. Ramshorns have been known to introduce parasites into the tank.
Diet: Mainly algae and detritus.
Maximum size: 1”
Similar in appearance to Apple Snails but usually smaller. The difference between them is that the shell of the Trapdoor is wider than it is high, and the spiral of the Trapdoor is more raised. They’re live-bearing snails, the eggs hatching inside the female’s shell. They tend to leave plants alone and are more temperate than tropical.
Diet: Algae and detritus
Maximum size: 1-2”
A snail observed to inhabit brackish/marine as well as freshwater environments. Some fishkeepers describe it as the “perfect” algae eater. Nerites are often enrolled to combat algae and are more active in tropical tanks.
Maximum size: about 1”
Pics: Bee Nerite shown top, Zebra Nerite shown bottom.
Most snails require harder, more alkaline water with PH around 7.5. Soft, acidic water will, for the most part, result in shell damage.
So, we’ve established that snails do have their uses in the aquarium, and that they’re not likely to eat your fish any time soon, but obviously, you need to control their numbers to some extent, otherwise you’ll be overrun! Below is a list of a few of the ways that you can control snail population:Fish
As previously mentioned, some species of fish, such as various cichlids or loaches, are known snail predators. Of course, it's vitally important that you carry out full, independent research to ensure any fish - snail predator or not - is suitable for your current fishkeeping ability, tank size and water chemistry, as well as compatible with your current stock before buying the fish.Food control
Watch the fish carefully at feeding times to ensure that you’re not overfeeding them and remove any leftovers after a few minutes. Use an algae magnet to clean the glass. This will force the snail population to adapt to the change in the supply of food and numbers should reduce as a result.The Lure
To put it another way – blanched lettuce/cucumber ;-) The trick is to weigh the cucumber/lettuce down in the tank – either by tying it to something to keep it down, or by jamming it underneath a rock or some décor. Leave the food in the tank overnight then, next morning, remove the veg and its snail collection.Chemicals
There are a variety of commercially available chemicals that are designed to kill snails. However, these are not generally recommended in anything but the very last resort, as any water additive that can kill snails may also pose a threat to the filter bacteria.
Preventing snails from getting into the aquarium
Is there anything I can do to stop the snails from getting into the tank at all?
If you want to avoid any snails getting into the tank in the first place, you’ll need to treat any and all newly acquired plants before adding them to the tank. Possibly the safest way to do this, is to dip the plants in a bath mixture of water and snail killer, leave them for a few hours, and rinse thoroughly before dipping them in dechloronated water (tank water would be ideal, if taken out of the tank) and adding the plants to the tank. Because you’re treating the plants outside of the tank, the snail killer won’t be any risk to the filter bacteria.
Some websites also recommend treating plants/décor with a weak bleach solution of 19 parts water to 1 part bleach for anything between 30 seconds and 2 minutes, but a bleach solution also risks the plants themselves and if even the faintest trace of bleach lingers on the plants, when they’re added to the tank, it can cause the fish serious health problems.
Many planted aquaria have a population of snails somewhere – if not on the glass, then hiding on plants or in the substrate, and unless you actively treat live plants in a manner that will kill the snails before you add the plants to the tank, you're likely to come across them in your aquarium sooner or later anyway. When they're properly managed, snails fit into an ecological niche and play a beneficial role in helping the keeper with tank maintenance - whether by cleaning the substrate of trapped fish food, or by cleaning the glass of an algae build-up, so a small snail population isn’t something to be worried about.