Ask the WWM Crew
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Yes, it's hard to imagine a natural aquatic setting without them, ancient, slimy gastropods slithering along, seemingly benignly, happily helping "keep the balance" by eating algae and detritus'¦ but are these lowly mollusks worthwhile, let alone worthy or your water garden? Maybe.
Weighed against their prodigious algae eating activity and keeping things stirred about are snails two principal drawbacks'¦ propensity for over-population and more serious penchant for disease transmission. Happily, there is much you can and should do re these twin problems if you're going to employ them.
And likely if you've planted out your system you've got some free (!) snails in the bargain. Though these ubiquitous mollusks are found in all manner of habitats, from hot springs in Iceland to mountains of 14,000 foot plus elevation, they are almost always found in association with aquatic plants. Not to fret. Here we'll discuss not just the practical utility of snails in captive ponds, but their economic eradication and control.
Snails, Part of the Mollusca:
Though there are many more species of Beetles, an examination of the snails, living and fossil, shows the Creator had a liking for the "stomach-footed" mollusks as well. Snails are literally everywhere, except the air; doing everything life-style wise. They inhabit icy mountains, the hottest, coolest, and deepest of waters. 'There are familiar forms that are free-living, annoying us by eating plant material in our gardens, aquatic and terrestrial. A few species actually swim in open seas. Still others are so small they make their living as interstitial organisms, living between sand grains. There are snail species that are deadly predators, fancy filter feeders, even parasites, internal and external on most invertebrate groups. Much more than you imagined I'll wager.
Snail fossils date back before the Devonian, some 380 million years ago, showing that a basic snail form has been around a very long time. Likely related to this group's long, stable existence is the important fact that snails act as hosts, vectors and space parasites for many other species of organisms. Some of these are critical to human health. Liver flukes, swimmer's itch, and schistosomiasis/bilharziasis are among the scourges that require certain snail species as intermediate hosts. Similarly there are known parasitic and infectious diseases of fishes and plants that are transmitted via snails. Snails can, indeed, be bad news; but here we'll ways to tip the scales in your favor.
Snails; The Good, The Bad, The Slimy:
There are many older aquatic gardening texts that laud the use of snails as scavengers; at times stating that the exception to their usefulness is the breeding of fishes, where snails may devour eggs and young.
Indeed many water garden supply businesses encourage their use is originating nutrient cycling. To start up new systems Socolof mentions the genus Ampullaria (Mystery, Apple Snails) for culturing infusoria, a microscopic amalgamation used as a first food for egglaying fishes. Snails bring along the starter culture for this critter bouillabaisse wherever they go.
Still another practical use of snails is as bio-assay organisms Especially air-breathing (versus strictly gill breathing) snail species, may function as such. When the water fouls they head to the surface.
But Are They Right For You, Your System? More to Consider:
What's the mystery? Most modern works surveyed point to the detractions of snail employment. For example, the 'Mystery' of the named snails in the genus Ampullaria used to be their mode of reproduction. I think the term really refers to whether they are alive or not, and possibly about to pollute your system with their stinky disintegration.
Cleaner-Uppers or Eather-Uppers? Regarding their claims of maintenance, in all honesty snails are not great scavengers. Most all species can and will become opportunistic omnivores; eating plants, other invertebrates, even other animals given the chance. To save my fishy 'sole', neither most catfishes nor snails do well exclusively on waste-products; they both should be purposely fed nutritious foodstuffs on a regular basis. Also, as regards blue-green algae (aka cyanobacteria.. And it may be any color) and diatom (brown) scums. Snails (actually not much) will eat this stuff. For these it's best to look to their root causes; inadequate filtration, too much light, over-fertilization, and correct accordingly.
Reproduction and How! You thought rabbits were bad? Most snails are functionally hermaphroditic, both male and female; everyone they meet is a hot date. Cross fertilization is the rule, though many small species are known to self-fertilize. A notable single-sex exception are the snails of the genus Ampullaria. Examples below.
One Last Minor Detail. Oh, and a real downside, they eat aquatic plants! Given a dearth of other materials most snails will gladly consume your purposeful aquatic greenery.
If You're Still Unconvinced and Going To Use Them:
Despite the previous list of negatives, you're still a snail lover? Good for you. The following pertinent notes apply to you and keeping your creepy-crawly friends.
About Snail Nutrition:
Remember; like the American Catfishes that folks try to relegate to a janitorial role, snails are not just pooper-scoopers. Learn what your species eats by reading and trying different foodstuffs, and regularly provide it.
About Unintentional Poisoning:
Beware of using clarifying agents, metal-based fish medications and most algicides as these are toxic to mollusks. By and large, snails can tolerate moderate salt exposure, to about one teaspoon per gallon. If you're a regular or treatment-salt user, I suggest adding the dose over a period of three days. Know that there are times and places where tap water contains appreciable amounts of copper, iron, other items you want to resist. It is suggested that you make frequent partial water changes, as opposed to ones.
Building Strong Shells, Calcium:
Snails need this element for their shells and metabolism. If you have soft (let's say less than 10 German degrees of hardness, or DH), acidic (under 7.0 pH) water, you will likely need supplementation of this alkaline earth mineral. Thin, pitted shells are generally indicative of calcium deficiency. There are several ways of supplying this essential matter. You can purchase granular calcium carbonate, add a little marble, limestone, dolomitic, coralline rock/gravel, or a little piece of 'food block' for your snails.
Snails as Jumpers:
I'm not joking. The larger snails can/will leave your system, especially at night. Keep your water level down a bit. If you find your aquatic snails out in the garden, plop them back in the water, even if they appear "all dried out". In all likelihood, your snail/s will recover.
Good Snails. Yes, There Are Some
Definitely the most important item on what snails you acquire is their source: CULTURED; that is, from a farm, breeder that has grown them in the absence of other organisms that you want to avoid. For instance the aforementioned flukes (roundworms) that are the cause of eye-fluke disease in fishes have a complex life-cycle, meaning they pass through one or more intermediate hosts, in this case a bird and a snail, before getting into fish hosts. By breeding and rearing snails in controlled environments, e.g. ones without birds, 'the cycle is broken'. Voila, no more parasites. The fish farms in Florida, U.S.A. have done an exemplary job of developing large healthy snails for the ornamental aquatics trade; their snails are clean. Check around your town, shops, internet suppliers, but don't risk "wild-collected" snails'¦. Snails that have been raised for several successive generations in captivity are far less likely to harbor pests & parasites. Never introduce wild caught snails to your system.
Some of the species commonly offered to the hobby and pertinent notes for those in the know:
Melanoides (Melania) tuberculata, the Malaysian Burrowing or Cornucopia Snail for it's long, cone-shaped shell. This species originates from East Africa to Southeast Asia. Overall color is olive to green with violet bands all over the shell. This snail is one of the best from a maintenance point of view. Some plant breeders even endorse them as non-plant chewers. They come out and scour the system at night, retreating by light of day. Their downside is that they are livebearers that can easily overrun a tank. These 2.5cm (1 in.) beauties are true tropicals however and will perish in water below 18C (@64F). Thus they are easily eliminated from temperate settings seasonally.
Ampullaria (now Pomacea) australis, A. caniculator, A. paludosa are the very large, Apple, Baseball or Golfball, Snails; the first two species hail from South America, the last is a Floridian. These brutes attain 6cm (2 1/2 inches); now that's a snail! They have long breathing tubes to aid respiration by poking out of the water's surface. These giants are ravenous plant eaters. They reproduce by laying their pink to orange eggs in a clump above the water's edge.
Ampullaria (Pomacea) cuprina, is the Mystery Snail of the U.S.. Many color varieties exist; from black, to flavistic yellow to pure albino forms. This is the snail for the aquatic gardener as far as I'm concerned. you can actually control Ampullaria proliferation as the sexes are separate and they're easily sexed. Males have a convex operculum, the trapdoor that they pull in to cover their soft bodies, and those of the females are concave, bent inward. For those up-to-the-last-minute know-it-all types, the New World Ampullaria species are now placed in the genus Pomacea.
Planorbis corneus, Marisa rotula, Segmentina victoriae and others are sold as Ramshorn Snails, immediately identifiable by the shape of their shells. Color ranges gray to a gorgeous deep red. Ramshorns are hermaphroditic and multiply faster than proverbial rabbits.
Viviparus malleatus the Japanese Livebearing Snail. This is a good old-timey outdoor pool and goldfish tank snail. 3cm (1 1/4"). Young born looking like miniature adults. Also great for coldwater systems are the Papershell Snail, Radix auricularia and the Australian Red Snail, Bulinus australianus.
Not so Good Snails That Are Offered In The Trade:
Physa species. To 3/4 inch. These things eat everything and reproduce like weeds. Also to be avoided the burrowing snails in the genus Stagnicola, freshwater limpets of several genera, &...
You Want Plants, But Forget The Snails? Prevention:
Avoiding snails has everything to do with acquiring initially clean and healthy plants, and then examining the same very carefully. With practice, snails and their egg masses can be easily spotted and scraped away with a thumb and a fingernail.
From the Latin "to cease": Beyond physical inspection and cleaning there are various molluscicide (snail-killing) baths or dips that can be recommended. Some of these are sold pre-mixed in the trade. I've found the ones based on aluminum sulfate (alum) and potassium permanganate (KMnO3) to be the most safe and effective.
Quarantine Value: If this were a perfect world we'd all have a quarantine system to stabilize, harden and rid new introductions of unwanted co-travelers. Should you inherit for a rich relation or win the lottery, a quarantine phase of a few weeks is recommended.
Wherefore Elsewhere? A mention of another source of snail infiltration, is 'live' freshwater foods. If you collect your own, be careful; commercially cultured, prepared foods are not as suspect.
You've Got Unwanted Snails'¦ How Do You Get Rid Of Them?
It is, of course, best to prevernt snails from getting into your ponds. But once you've got them, how can you give them the boot? Methods of eradication fall into the following natural order, from most to least desirable: Biological, Manual, and Chemical.
These are the best lines of offense in reducing snail populations. Note I didn't say wiping out snails entirely. Don't be disappointed if what you end up with is a predator/prey relationship with fat hunters and scarce, but present snails.
Cichlids for this job include the lowly Convict/Pink Congo Cichlid to the specialized African types like Haplochromis placodon, Chilotilapia rhoadesi, Lamprologus tetracanthus among others. As usual with this diverse family of freshwater fishes, you may be minus the snails, traded for cichlid-destroyed plants, excavation... Be wary of keeping large cichlids and live plants together for long.
Snail-Eating Turtles: I mention in an effort to be thorough. In the old pet-fish store days we used to 'lease/lend' such turtles to aquarists who wanted to rid their systems of snails. They worked and are at times still available for hire. Check with other folks who keep ponds in your area as well'¦ maybe they can lend you one of theirs for the job.
Various Fishes may bug snails; possibly to death. Bettas and their relatives, the Gouramis; swordtails, platies & guppies... other choices abound depending on your climate, water quality.
Waterfowl May Be a Worthwhile Try: For temporary snail eradication duty; it may be that their filthiness is tolerable.
Manual Means: Feeding Trays, Forceps...
Mano a mano, as in by hand. It may seem tedious, because it is! Sometimes though, the physical removal of such pests is not only the best way to keep them in control, but the only way.
Don't just sit/stand there with that net in your hand. Think! Laying out some freezer-burned, or boiled vegetable material or sinking pellet food in a glass dish in the middle of the system at nightfall will aid you in gathering/baiting your prey. In the morning you'll find gazillions of snails concentrated in the area where they can be easily removed.
Chemical Control: A Dangerous Approach
This is the least desirable method of snail eradication, being too toxic and dangerous. If you're going to resort to poisoning, do attempt to thin the herd of snails first by the methods described under physical removal; baiting and hand-netting.
If you consider semi un-selective poisoning to be the modern way to rid your system of snails, do purchase a product specifically formulated for this purpose and utilize exactly per instructions. In particularly, be accurate as to how many real gallons of water are in the system. There are about 7.5 gallons per cubic foot of water, but a better approximation can be had by "timing" the filling of a known volume (e.g. five gallon "pickle" bucket) and timing the time it takes to fill the system.
Those pretty blue copper compounds labeled as snail-i-cides are the most efficacious. Still, do provide a ready pool to remove your fishes, other animals to should they suffer from the treatment. Be wary of nicotine and organophosphate treatments
Zapping Your Snails: That's Re-Volting:
I'll just mention in passing the various schema I've run across utilizing direct and even alternating current (yep, that's electricity) for zapping snails. Don't do this. I'd skip trying mollusk electrocution with or without fishes in the system. In fact, if you are using economic poisons, you'd do well to remove the fishes during the 'treatment', if at all possible.
Are aquatic snails necessary for a watergarden? No. Are they even desirable? In some cases'¦ some species'¦ maybe. Their presence can indeed add interest, help with algal control, and facilitate nutrient cycling. But snail use does have definite downsides. Many types of snails are uncontrollably prolific and they are known disease carriers for fishes, humans, and plants.
If you don't want snails:
1) Carefully look over, dip, if you can quarantine all new plant introductions for a few weeks.
2) Utilize bio-controls like those listed above,
3) Dedicate yourself to routine manual search, removal/destruction of their numbers.
4) Or least desirably, wage a semi-selective chemical poison war, hopefully negatively impacting what you want to eliminate while not harming what you hold dear.
Most growers of aquatic plants will tell you that snails can quickly multiply and destroy a system if not kept in check. My advice to earnest aquatic gardeners is to avoid them.
Anon. 1975. The Snail- Aquarium Aid of Pest? Aquarium Digest Intl., 2(1):75.
Barnes, Robert, 1987. Invertebrate Zoology, 5th Ed. Saunders.
Forsyth, Doug. 1988. A Practical Use For Snails!! The Nekton 8/88.
Masters, Charles O. 1981. Livebearing Snails. TFH 11/81.
Masters, Charles O. 1984. The Great Pond Snails. TFH 7/84.
Pointier, Gloria & Jean Pierre. Ampullarid snails: forgotten creatures of the freshwater world. TFH 7/95.
Socolof, Ross B. 1980. Snail Update & a New Pale Snail. FAMA 10/80.
Starmuhlner, Ferdinand. 1989. The Alluring Apple Snails. TFH 1/89.
Werner, Ewe. Snails in the Aquarium. TFH 9/83.