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Issue: August 2009

Taming the Tenacious Trumpet Snail

Author: Tom Lorenz

LORE T 0809
Photographer: MP. & C. Piednoir
The ability to survive in almost all water conditions, breed easily, and clean up after fish sounds like the recipe for a perfect invertebrate—but there is certainly such a thing as being overly successful. Our inquiring author details a tiny resident that, while providing numerous benefits, may present an equal amount of trouble due to its knack for overpopulation.

In the song “El Condor Pasa,” Paul Simon wrote, “I’d rather be a sparrow than a snail.” Sure, flight and larger size seem like an obvious argument for preferring the former, but perseverance and success are admirable traits as well, traits that are common to many species of the humble snail. In fact, to be obnoxious and list two more quotes, preachers and evolutionary biologists even agree on the survival skills of the snail. A 19th-century preacher, Charles H. Spurgeon, stated that, “By perseverance the snail reached the ark,” and Charles Darwin noted the only living animals he found in a brackish stretch of water in an uninhabited desert were aquatic snails. Take that, sparrows!

In the aquarium hobby, there is one species that stands above all the rest as a snail of perseverance. The red-rimmed melania or trumpet snail Melanoides tuberculatus is a hardy and common species of snail from Southeast Asia found in thousands of aquaria, probably numbering in the millions.

Trumpet snails are in the family Thiaridae and are naturally found in subtropical and tropical areas of Asia and Africa. They have a third and very descriptive name as well—the Malaysian livebearing snail. These snails can reproduce both sexually and through parthenogenesis, starting at a size as small as 10 millimeters! Instead of eggs, these snails give birth to as many as 70 live young at a time. With a reproductive strategy like this, you might guess that they can increase in numbers rapidly. And you’d be right.

From birth, these snails have their first two whorls and are ready to take on the world (or your aquarium). They don’t grow too large, usually not much more than an inch, but they can exceed two inches in deep waters in nature. Their prolific existence is also not limited by salinity. They thrive in freshwater to extremely brackish conditions. Many other freshwater snails do poorly with salt, and many saltwater snails do poorly with water that is too fresh.

This also isn’t the most finicky of snails when it comes to diet. Algae, detritus, and excess fish food are all on the menu. Because of their subtropical range, they can deal with temperatures dropping well below room temperature, even approaching freezing.

Such a tough animal seems like it could be a great or dangerous thing to have in an aquarium, but the fact is that the trumpet snail is both. With the following knowledge you can decide if you want to try keeping them, taming them, or avoiding them all together.

 
Benefits

The good side of keeping these snails is their hardiness and appetites. Few water conditions are hated by these critters, and few meals are passed up. Algae and excess fish food are scourges of most aquariums, and both of these are relished by trumpet snails. It is much healthier for wasted food to be converted into more snails as opposed to extra nitrogenous waste for your biofilter load.

The best part about their feeding habits is the fact they avoid eating live plants. Another thing appreciated by some live plants is the loosening of the gravel, which is caused by these burrowing snails. Most other snail choices (including pond snails that sneak in on live plants) don’t have these desirable qualities. Excess dead plant material is also nicely eaten away by these omnivores, adding to their tempting resume as planted-tank additions.

Dream come true, right? Well, nothing succeeds like success—and nothing succeeds more like extreme success! These snails are so good at eating and making more snails that it’s nothing short of astounding. Trumpet snails can find food everywhere, from an inch above the surface of the water to the bottom of the gravel bed. Their feet hold strong in currents, and they move relatively fast for a snail (see some time-elapsed videos on the Internet for amazing evidence of this!). They can also endure the nipping of small fishes and the crushing jaws of moderately sized fishes (although I’ll discuss specialized predators soon).

 
Troublesome Trumpets?

But wait, is this a problem? It is if you let it get too far. These numbers can get so high that you have a whole new group of animals adding to your bioload. What is worse than that is what can happen to your filter intakes. If you have powerheads, these snails can rapidly clog up these filters and even find their way to the impellers. Once up against the impellers, you can get a horrible rattling sound and even a broken impeller. Also, you never know exactly how many you have because of their proclivity to hide in the gravel. Turning on the lights in the middle of the night has brought a gasp to more than one aquarist (they often come out in force at night). Cosmetically, they can get in the way of the look you want for your tank. Not everyone wants a snail tank.

No pet store has avoided that dreaded question of, “How do I get rid of these snails?” Tales of snails surviving excessive salt and even dried-up gravel abound. Overheating, cooling, and molten lava all fail to slow their progress. Okay, maybe not the lava, but these are indeed amazing survivors that just don’t go away without a fight.

What is the best remedy for a species that is so tough and prolific? Is it a fight that can be won? Is it one worth fighting? First of all, it is possible, but you may be better off just keeping the numbers low instead of eradicating them. Low populations give you the benefits without the major problems.

If you want to eradicate them, there are plenty of options here, too. You can empty and bleach a tank, which is dramatic. More dramatic (and possibly the worst decision) is to use over-the-counter chemicals that claim to specifically kill snails. Many of these chemicals include copper, which is actually toxic to just about any living thing. Luckily for the fish, they’re bigger. That means they won’t die at certain copper levels, but it doesn’t mean they won’t feel any sub-lethal effects. Another option to affect snail success is water conditions. When water gets to a certain level of softness and low pH (below neutral), these snails have trouble building their shells.

But the best solution out of all of these choices is to feed your fish less! Excessive feeding is cleaned up by these snails, but if you abuse this benefit they offer, they’ll take all that extra food and make extra snails. Cut things back and the snail numbers will follow suit. For the impatient, you can put a large piece of lettuce in the aquarium at night to snag large numbers of snails at a time, speeding up the process.

 
Snail Assassins

Should you want a more gladiator-type approach, there are fish that relish the chance at eating snails. With all those whorls, these are actually not the easiest snails to eat, even for snail specialists. Fish as ravenous as African cichlids actually leave the snails alone for the most part. But some fish are very good at crushing, shucking, and biting right through even snails like this.

Certain species of loaches are famous snail eaters. Clown, skunk, and yoyo loaches all are employed for this cause, and there is long list of other loach species that will do the job as well. With a quick twitch, these snail assassins rip the snail right out of the shell. Also, clown loaches (and probably others) are known to enjoy eating snail eggs. Therefore, if you have non-livebearing snails, these will be eliminated even faster! The downside of this is aggression to your other fishes. The subocular spines of loaches are wicked weapons, and many species squabble with each other and with other fishes.

A more simple and brutal approach is to crush the snail. With hard-bodied prey being abundant all over the Earth, there are also fish with snail-crushing jaws everywhere. Many cichlids can develop the skill for ripping snails out in loach-like fashion. Species as different as yellow labs Labidochromis caeruleus and Haitian cichlids Nandopsis haitiensis do this. There are, however, snail-eating cichlid specialists that have jaws custom-made for crushing snails. The buffalo cichlid Steatocranus casuarius and (the endangered) Herichthys minckleyi have powerful pharyngeal jaws specially made to crush snails. Other cichlids have these jaws too, but there is an arms race between sturdy snail shells and powerful snail-crushing jaws. The easy solution to this is to have a large fish for the job. Large, generalist-feeding cichlids like red devils and Texas cichlids don’t specialize in snails, but they will demolish small snails like M. tuberculatus.

Pharyngeal jaws are great tools for eating snails, but what might be even better is a beak! Puffers tear apart snail shells the way large parrots tear apart hard seeds. Except for large snails and small puffers, this matchup is almost always in favor of a fat and happy pufferfish. Like the snail-eating loaches, puffers not only eat snails, they do so con gusto! Again, as with both the cichlids and the loaches, there are aggression issues to be considered. Some puffers are downright insane and appallingly persistent with their dispatching of tankmates.

A final note on getting hired fish thugs to solve your problem—once you get a snail specialist, you’ve got another mouth to feed. Also, if there was anything you liked about having a couple of snails, you’re out of luck. These fish don’t tend to leave any survivors to tell the tale.

 
Trouble Beyond the Box

The success of these snails can actually be a problem on a scale much larger than your aquarium, believe it or not. While having a powerhead ruined or a tank overrun is annoying, imagine impacting an ecosystem or spreading disease. This is a little more concerning and not as easy to solve as adding a few loaches!

Trumpet snails do, in fact, thrive outside of the aquarium as well. If you live anywhere that has mild winters, you may have a waterway that has been invaded by these snails. Texas, Florida, and Louisiana are a few states that have established populations of these snails, and they can get out of control in the wild just like in the aquarium. In St. John’s River in Florida, densities have been reported as high as 10,000 per square meter (Thompson, 2004)! And you thought you had a snail infestation!

This, of course, affects native species and natural food webs, but there’s an added issue here that really hits home for humans. Trumpet snails are vectors for disease. While the complex life cycles of parasites means you won’t get sick from your aquarium snails, it doesn’t mean that these snails can’t carry disease in the wild. Chinese liver fluke and the Oriental lung fluke both infect humans and are passed from this snail to a crustacean in the wild. Living in Louisiana, I eat plenty of crustaceans, but it’s best to avoid eating them raw if you can help it (not that I need to tell most of you that)!

It’s fun to spin a yarn involving a few quotes, snail predators, and parasite scares, but the ultimate lesson on this species is one of moderation. Don’t feed your aquarium inhabitants too much and you shouldn’t have any problems. If you have snails and don’t want them around, get your hired gun (cichlid, loach, puffer, or other). If you like them, you can appreciate their useful side and their potential to be part of your small version of an ecosystem.
Either way, on the list of species for us to worry about disappearing, this one may be neck and neck with the cockroach. You can’t help but admire such tenacity!

 
References & Resources

Gulf States Marine Commission: http://nis.gsmfc.org/nis_factsheet.php?toc_id=144

Thompson, Fred G. 2004. “An Identification Manual for the Freshwater Snails of Florida.” Florida Museum of Natural History: www.flmnh.ufl.edu/malacology/fl-snail/snails1.htm



See the full article on TFH Digital http://www.tfhdigital.com/tfh/200908/#pg81

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