There’s something almost surreal about the way an apple snail goes about the serious business of laying its eggs. I consider myself fortunate and privileged to have witnessed this long and drawn-out process countless times throughout the years. Yet, no matter how often I see these large snails doing their stuff, it still fascinates me.
The fact is that apple snails are special in many ways, and even if their reproductive strategy were straightforward, there can be no denying that these magnificent creatures are, by far, the most impressive mollusks found in freshwater aquaria and ponds. Is this the view of an openly biased apple snail fan? Perhaps. But read on, and make up your own mind.
The golden apple snail lays its eggs above the water. Photo by John Dawes
Pet or Pest?
Apple snails (Pomacea spp.) are widely accused of wreaking havoc wherever they are introduced, and they have been introduced into numerous countries and regions outside their natural ranges. The aquarium industry and hobby are often the main targets when it comes to accusations regarding these introductions, and there can be no doubt that they have, indeed, been the guilty parties in some instances, but most certainly not in all. During the 1980s, for example, the channelled apple snail (P. canaliculata) was introduced into Taiwan for culinary purposes. It didn’t meet with the expected acceptance and eventually escaped into the natural environment. From there, it spread to other countries in the region, among them Cambodia, southern China, Hong Kong, Indonesia, Japan, the Philippines and Thailand. Reports have also emerged of its spread into Australia and India, while the region of Spain around the Rio Ebro delta has suffered severely in recent years. The snail is also already present in Hawaii and other non-native United States locations.
This species’ voracious appetite for most types of plants means that it can seriously damage food crops and other vegetation wherever it establishes a foothold, making it a serious pest. Other members of the canaliculata species complex also have similar dietary habits.
On the other hand, the spike-topped apple snail (P. diffusa) and the golden or mystery apple snail (P. bridgesii), also, confusingly, sometimes referred to as the spike-topped apple snail, prefer dead or rotting vegetation and will leave healthy plants, except soft and delicate ones, untouched if there are other food sources available. As a result, they don’t have the same pest qualities of their larger, all-consuming relatives and, thus, make much “safer” pets. Even so, every care must be taken to ensure that specimens don’t escape into the wild, where they may reproduce and spread, irrespective of their relatively non-destructive diet.
Apples in the Aquarium
Perhaps it’s because of the bad press concerning crop damage, or perhaps it’s the full details are not known, but whatever the case, apple snails have a generally poor reputation in some quarters. As a result, many aquarists believe that these mollusks are far from ideal aquarium inhabitants. But how true is this?
Pomacea diffusa mating. Photo by John Dawes
The answer is that it very much depends on what the aquarist is looking for. If you want to enjoy a well-planted aquarium housing apple snails, then there’s no doubt that the species to avoid at all costs are P. canaliculata and its closest relatives, owing to their voracious, plant-eating habits.
Even those plants that are generally unpalatable to plant-eating fish, such as Java fern (Microsorum pteropus) and Java moss (Taxiphyllum barbieri), are not immune from attack by these species. Indeed, species of the P. canaliculata complex will eat virtually anything, not just plants. They will even consume dead or dying fish, to say nothing of vegetables like lettuce, cucumber, zucchini and carrots, and the list goes on and on. However, if you are prepared to decorate your aquarium with artificial plants, then there’s no problem.
In sharp contrast, the most common apple snail species, P. diffusa, is not an obligate plant destroyer. In fact, it is sometimes reported that this species can actually starve to death in a well-planted aquarium if it’s not offered alternative foods. Pomacea diffusa does not take kindly to tough foods, but fish pellets, flakes, boiled lettuce and spinach will be readily accepted. So, this is undoubtedly the species to choose for the average home aquarium.
It’s difficult to over-feed apple snails, but it’s not impossible. Therefore, a careful lookout must be maintained to ensure that food is not allowed to remain in the water until it begins to rot. Given that apple snails are hardy creatures and breathe atmospheric air via their siphon, they can withstand less-than-ideal water conditions, but any fish housed with them can’t, so provide good filtration and aeration. The choice of filtration and aeration can be quite flexible, as long as water clarity and quality are maintained. Although apple snails are generally found in placid waters, they can undoubtedly withstand water movement, but this doesn’t need to be over-vigorous.
Apple snails require calcium to produce shell material. Therefore, they prefer hard water, but they can survive in softer (but not ultra-soft) conditions. If the water is too low in calcium, holes will begin to appear on the shell and its overall robustness will diminish. Consequently, when choosing fish mates for your apple snails, it’s sensible to go for types that are comfortable in relatively hard, preferably alkaline, water. It also helps to provide cuttlebone as a source of calcium, as well calcium-rich vegetables, such as kale.
In terms of tank size, this depends on the number of snails you keep and on whether they are kept on their own or with fish. It’s difficult to establish strict guidelines because much also depends on the water quality provided and the snails’ ability to withstand parameters that would normally not be acceptable for fish keeping. However, as a rough guide, allow about 21/2 gallons for each medium-sized snail, but take account of the fact that medium-sized snails will soon become fully sized individuals, given appropriate conditions.
Apple snails tolerate a very wide temperature range, and anything between 65 and 82 degrees Fahrenheit will be fine. Of course, activity, feeding and waste-producing rates will all be higher nearer the top end of the range.
In terms of pH, anything between 7.0 and 8.0 is perfectly acceptable. As with other parameters, apple snails are tolerant of a wide water-hardness range, with medium-hard to hard water being suitable (dGH between 8 and 30).
The genus Pomacea is sometimes reported to contain more than 100 species. However, their taxonomy is complex, and with environmental conditions resulting in changes in overall shape and other characteristics, it’s quite impossible to determine at the moment exactly how many valid species there are and how many names are just synonymies, i.e. different names for the same species. Until DNA studies are performed on each, we won’t know for sure. One thing is pretty certain: the final number will be considerably fewer than 100.
Pomacea diffusa, the blue variety. Photo by John Dawes
Here are a few examples that highlight some of the ambiguities.
I used to believe I had kept two species of apple snail: the channelled apple snail (P. canaliculata) and the spike-topped apple or mystery snail (P. bridgesii). Now, I’m not so sure. This doubt relates to the fact that apple snail classification is a complex and debated affair.
For example, the spike-topped apple snail, which I refer to as P. bridgesii above, also appears as P. diffusa. It is also still reported as a species consisting of two subspecies: P. bridgesii bridgesii and P. bridgesii diffusa. However, a paper published by T. Pain in 1960 argued that the former was larger and had a restricted range (Rio Grande, Reyes River at Beni, in Bolivia), while the latter, smaller P. diffusa enjoyed a wider distribution throughout the Amazon basin.
In 2003, it was suggested by R.H. Cowie and S.C. Thiengo that P. b. diffusa warranted recognition as a separate species, and this was confirmed by genetic analysis in 2007 by Cowie, working with T.A. Rawlings, K.A. Hayes and T.M. Collins.
Historically, the species most frequently reported in the trade and hobby has been P. bridgesii, but it is now believed that true P. bridgesii are rare and that the common species is P. diffusa.
The situation regarding P. canaliculata is also a little convoluted. It belongs to what is referred to as the P. canaliculata-insularum group, complex or clade, consisting of, at least, the following: P. canaliculata, P. insularum, P. lineata, P. doliodes, P. haustrum and P. maculata (this last species is also sometimes referred to as P. gigas). The species most often encountered are P. canaliculata and P. insularum, but P. haustrum and P. maculata may also be available from time to time. It appears that the golden snails from this species complex that occur in the trade and hobby are P. canaliculata.
In addition, the Florida or Cuba apple snail (P. paludosa), which does not belong to the P. canaliculata-insularum complex, may occasionally occur within the trade and hobby. To the best of my knowledge, no color forms of this species have been created for home aquaria or ponds.
In summary, it seems that the majority of apple snails available to hobbyists are P. diffusa (in various colors) and P. canaliculata (in both the wild type and golden varieties).
Apple snails are not just popular in the U.S. They have also had an army of admirers in Europe, with the golden variety far outstripping all others in terms of sales. This, at least, was the situation ever since apple snails began appearing on the market. Then, without any warning, all imports were banned by the Spanish authorities in the summer of 2011. This was swiftly followed by a U-turn with respect to Pomacea bridgesii (which, in view of the comments made above, may be P. diffusa), even more swiftly followed by yet another U-turn re-banning imports of all apple snails, irrespective of species, for home aquaria. Subsequently, in December 2011, Spain published a Royal Decree in which the entire Pomacea genus was featured in a list of prohibited animals and plants deemed to be invasive.
Shortly after this occurred, the European Commission—via its plant committee—launched its own apple snail review, followed by an Implementing Decision (published on December 8, 2012), which took the Spanish lead and banned imports of all apple snails into Europe. There was even talk of banning aquatic plant imports if these originated in countries and/or farms where apple snails were present. Such a drastic move obviously raised serious concerns among all stakeholders, who lobbied for a reassessment of the situation before any final decision was taken.
As things stand at the time of writing, the pan-European ban is in place and it will continue to be so for the foreseeable future. Nonetheless, we can’t discount the possibility that moves will be initiated at some stage to review the situation, particularly with regard to some of the more northern European countries, where apple snails cannot survive the harsh winters and don’t, therefore, represent the threat they do in the more southern European Member States.
For the moment, though, European aquarists cannot buy or own apple snails of any species. Further, hobbyists who possessed apple snails prior to the European legislation were deemed to be in breach of the law and had to destroy their stocks.
Despite the fact that the dietary habits and invasive potential of some species of apple snails have caused, and are causing, problems in some regions of the world, there can no denying that they remain fascinating, beautiful and relatively long-lived creatures (with an average lifespan of 2 to 3 years) worthy of serious consideration by any aquarist prepared to shoulder the responsibilities of owning these impressive mollusks, law permitting, of course.
Sadly, given that I now live in Spain, I can no longer keep apple snails. Like my fellow aquarium and pond owners in Europe, I had, most regretfully, to destroy my stocks following the ban on the sale and ownership of all Pomacea species. Nonetheless, I remain a strong admirer, and should the law be changed at some stage in the future, I will once more become a devoted snail keeper. Until then, I have my memories and my photographs. They may be poor substitutes for the real thing, but at least, no one can ban them!
John Dawes is an internationally renowned authority on fish, aquaria, ponds and water gardening. Formerly a teacher, and then a lecturer at the University of Bath, England, he has, since 1983, been a freelance author, editor and international ornamental aquatic industry consultant. His books have been published all over the world. John holds a joint honors degree in biology and geology and a certificate in education. He is also a fellow of the Zoological Society of London and The Linnean Society of London, a member of the Society of Biology (London) and a chartered biologist.