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The freshwater snails of the genus Pomacea are commonly known as the apple snails (or mystery snails outside of the UK). They were once the most popular snail for the community aquarium. That all changed in 2012 when the European Union banned the public and private sale of apple snails within the EU. This law was introduced after the discovery of a feral population in Spain that was destroying rice farms. Fast forward to 2021, and in January this year the department of fisheries and rural affairs (DEFRA) lifted the ban in the majority of the UK. When translating EU directives into GB law (post brexit), DEFRA decided apple snails do not pose a threat in the UK. The law has only been changed in England, Scotland and Wales however, as Northern Ireland remains within the remit of the EU. For some fishkeepers, seeing apple snails available once again will bring back good memories. For others, this will be the first time they’ve had the opportunity to keep these curious creatures!
The latin name of an animal often gives a hidden insight in to a physical attribute that can be used to identify it. Pomacea is adapted from the latin pomum (first referring to all fruit, before more specifically being used for apples). Those who speak French would also recognise pomme as the translation for apple. It is not difficult to understand why species in Pomacea are named as such. Their large, roundish shell can easily be recognised to their similarity to the popular fruit. With some species growing up to 15cm, they can even match their namesake in size!
Apple snails also have a couple of special adaptations giving them an advantage out of water. Although being predominantly aquatic and using a gill to breath underwater, they also have a lung allowing them to breath air. This lung has an expandable siphon that allows them to remain underwater and reach the surface, acting like a snorkel tube. This becomes useful if the saturated oxygen levels of the water are low and they do not want to be predated at the surface by birds and other land animals. Secondly, when water levels deplete during the dry season, apple snails can bury themselves in the mud and aestivate (summer hibernate). To keep themselves from drying out completely, they have a hard shell door (the operculum) to provide a tight seal. Interestingly, the operculum is the same scientific term given for a fish’s gill cover. Fish use their operculums to push water through their gills. Most sharks and other primitive fish lack these hard gill covers, which is why they need to constantly swim in order to flow water over their gills.
Where are apple snails from?
There are more than 150 species of freshwater snails known as apple snails. They are native to South America and Africa. Species from the genus Pomacea are the snails most commonly kept in aquariums and are native to South America. There is some confusion as to the exact species sold in aquariums stores. The general consensus is Pomacea diffusa is most commonly seen for sale but other notable species include P. canaliculata and P. bridgesii.
The popularity of the apple snail has led the species to establish feral populations across the world. The aquarium industry has a lot to blame for these alien populations. Unwanted animals released by fishkeepers or breeding facilities which have had a breach are the most likely source. But there are other industries that are also to blame. A famous case was an apple snail facility in Taiwan, built in the 1980’s to grow snails as a food source. The snails were able to escape, and similar to what is now happening in Spain, the feral populations decimated the rice farms. This feral population then spread to other South-East Asian countries and has caused long-term problems across these regions. Hawaii is another country where accidental release of apple snails have caused major damage to native flora and fauna.
What colours do apple snails come in?
Apple snails can be found in a variety of colours and patterns. In the wild, apple snails have a dark brown striped shell and a dark foot. When looking for apple snails in an aquarium book or an internet search, the wild type is not usually what will show up first. The most popular and common colour is a bright golden shell with a lightly coloured foot, vastly different to their wild cousin. This is the colour usually seen for sale in aquarium shops. Rarer colours that are sometimes available include ivory (described as an albino gold), blue (dark almost purple foot with an off-white shell) and jade (dark footed but golden shell). Over time, breeders have been able to establish different colour morphs through selective breeding. Some of the more obscurely coloured apple snails are highly sought after and can demand a high price! They can all be mixed in a community aquarium but if looking to breed them, bear in mind mixing colours can often lead the offspring to revert back to wild-type.
Keeping apple snails in an aquarium
Apple snails make a great addition to the community aquarium. They do not pose a risk to fish or shrimp species, tend not to attack plants and do a good job at eating algae. Providing a good quality algae wafer (such as NT Labs Pro-f Algae Wafers) to supplement their diet should keep them from nibbling at plants. Pro-f Algae Wafers contain spirulina, a ‘superfood’ algae that contains high levels of calcium - perfect for maintaining shell health and development. Expect apple snails to grow between 5-6cm in an aquarium, depending on species.
Apple snails are not too demanding with water parameters out of the normal levels to check. Keeping ammonia, nitrite and nitrate levels low is always important as it is with any aquatic species. Whilst they are unfussy with water conditions, it is important to monitor the hardness of the water. A low general hardness (GH) means there is a lack of calcium and magnesium in the water (soft water). Apple snails absorb calcium from the water to grow and maintain their shell, so ensure the GH is kept in the ‘hard water’ range of 8-18dGH.
Along with hard water, it is recommended to keep the pH above neutral (pH 7.0) to maintain shell strength. In acidic conditions, the calcium carbonate shell will weaken in a form of neutralisation reaction. Regular testing with NT Labs Aquarium Lab test kits will ensure the water conditions remain optimal - giving ample time to remedy any adjustments the aquarium water may need. The apple snails temperature range is wide and they are happy in water kept between 18-28°C, somewhere in the middle being the ideal. It means they are quite suited for unheated aquariums kept indoors as well as tropical tanks.
Like all invertebrates, apple snails are very sensitive to treatments that contain copper. It is important to check the ingredients of any fish medication before commencing treatment. All NT Labs Aquarium treatments are well labelled to whether they are plant safe, shrimp safe and/or filter safe. If the treatment is not marked as shrimp safe, it is safe to assume this contains copper and so should be avoided in an aquarium containing snails.
Breeding apple snails at home
Apple snails are easy to breed in the home aquarium. Luckily, they are easier to control than pest species like the Malaysian trumpet snail. Unlike most species of snails and slugs (gastropoda) which are hermaphrodites (possesses both male and female sexual organs), apple snails are either male or female (dioecious). Whilst male and female apple snails can be told apart, it is not too obvious from their exterior. Male organs are visible near the gill atop their mantle but are most obvious during mating. Once the eggs have been internally fertilised, the female apple snail will climb out of the water to lay their eggs. The eggs are laid into a bright pink sack and develop out of water. Here they are out of aquatic predators way until they hatch and re-enter the water to start their life. To prevent a population boom of apple snails, simply remove the pink egg jelly, leave out to dry, and discard in household rubbish.
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