Controlling Pest Snails

By C. Moormann

Some suggestions on getting rid of pest snails.

I have found that bringing home plants will in most cases bring along some pest snails and eliminating the snails if they do become a problem could be useful. The worst snails I have ever seen infected my tanks about 2 years ago and one was a tiny flat red ramshorn that I had never seen in over 30 years of fish keeping. They hang on the sides of the tanks and resemble little red ears or possibly some tiny red Fiesta dinner plates. Another type was a tiny brown snail that looked like a thin and miniature version of a pond snail. They resemble the tiny young of the Maylaysian Trumpet Snail -- a snail so ubiquitous that it can be refered to by its initials: MTS. Both of these new invaders are new enough to me that I do not have a name only the description. The red ramshorns appear to prefer to lay their eggs on floating plants and I suspect the other pest is a livebearing species. Both came to me from a friend that gave me some of his excess plants. They tend to hide in floating plants which I propagated in one tank and when I put my excess plants in other tanks, they got well established before I really saw them. I have nothing against plant people but it appears that a common denominator is that they have a unique undertanding of snail control -- they don't try to eliminate them -- they kind of live in a state of denial as to the negative effects of snails. The guy I got the snails from assured me that the plants were 'snail free' and after I complained of the infection his expanation was that he was aware of them but did not consider them a problem to his tanks and by extension to mine. These plant growers usually have some loaches in the tanks that keep the populations low but always there. They also feed very little and do not see the type of explosion in snail growth I experience when I feed fish in breeding and growout tanks.
MTS (the Malaysian Trumpet Snail and probably the #1 offender) When uncontrolled, the MTS will cover the entire bottom with moving snail shells and their tiny young look like pepper on the surface and are easy to spread with any netting of fish or movement of plants. Some people think they perform a useful service in keeping the gravel aerated or something. If you are trying to grow out fry or condition fish for breeding it is desireable to be able to leave a little extra food in the tank for the fish to pick at since you probably don't have the time to feed 6 or 8 times a day. With an uncontrolled population of snails the extra food just goes into more snail protein. Some lame suggestions include using loaches, placing food out in a specific area and netting them out, or turning off the circulation to the tank and netting them off the glass when they go up for air. Using these methods will reduce to population but not eliminate them. When I bought my pet shop I found MTS in all tanks and even a shorter reddish-brown variety I had never seen before. After visiting my wholesaler and viewing his tanks, I knew how they got there. He had them in almost every tank and apparantly when netting out fish and bagging them, a few small snails were there invisibly or with some gravel netted out in catching the fish. The poor LFS owner is usually pretty busy and just floats the bags in the tanks and then later cuts open the bag and fish, water, and stowaway snails enter the tanks. The poor busy aquarist repeats the mistanke when he brings home fish. They do not come in with fish food or with brand new gravel -- examples of some lame excuses I have heard.

Now for a discussion of possible methods of MTS snail elimination:
1. Copper
Copper is frequently recommended and I once tried it. I bought a small bottle and put some MTS in a bowl of water and added a few drops of the copper and the snails were all dead the next day. I tried to scale up the prescription to some of my larger tanks and found that I could double or triple the dosage in the bowl and found the snails still thriving in the tanks. A careful reading of the copper cure bottle showed that all activated carbon should be removed -- but I did not have any in the tanks. Apparantly the organics in the tank such as the crap in the filters and gravel is a type of carbon and has the same copper removal characteristics and locks up the copper leaving the snails unaffected. Dumping larger doses of copper into the tanks seems dangerous and expensive and although the copper cure was fairly cheap a copper test kit was very expensive. I had over 15000 gallons of water at the time and using copper was not going to be possible.
2. Salt
Using rock salt had some contradictory results as it appeared that high doses of the salt killed most of the snails but has the effect of making the snails close up and a few must have very effective trapdoors and can seal up the door and wait for better conditions. You have to use a lot of salt and wait for at least a month to be sure you get them all. A lower concentration (about 1/2 ocean levels) of salt appears more effective in that you can use the tank for guppies or mollies and the snails come out but experience some type of slow organ failure over a period of months. Unfortunately I cannot prescribe the exact concentration or time of exposure -- remember that too much salt will cause some of them to close up and wait you out. Other chemicals such as chlorine or ammonia are relatively short-lived and the MTS can wait them out.
3. Snail eating animals/fish
Loaches are a frequently advised method that will not work as the large snails will just close up and if you are feeding the tank, the loaches will just eat the food and not all of the snails. I even tried horsefaced loaches once and they got over 4 inches long and were usually buried in the gravel but I never saw a dent in the MTS population. I have heard that certain turtles and puffers could do the job but they are expensive and will eat fish also so are unlikely candidates. If someone will buy me some neat turtles and/or puffers I will perform the experiment. Large koi will do the trick if they are at least 8 inches long. They spend all day long sucking up and mouthing gravel and the glass and appear to be able to get the big ones also given enough time for all the MTS to come up and get attacked. I use this method and will see even large MTS shells floating up at the surface with a small amount of the snail still in the point of the shell indicating that the main body has been sucked out. If there are a lot of snails or a lot of gravel and places to hide this may take a very long time but at least you will not have to worry about spreading the baby snails as the large koi will get them for sure -- unfortunately the large koi can eat small fish also so keep that in mind. This has been my weapon of choice for years but occasionally it has come back to bite me as the time I had over 500 neons disappear in a week when the koi in the tank grew from a small size where he did not bother the fish then all of a sudden reached critical mass and became a small great white shark. Having a small koi or loach in a tank will help get the little ones that get into your tanks when you are careless and they also keep filter tube screens clean and are good scavengers. They will dig up and eat your plants though.
4. Baking the gravel
This is the preferred method to really clear out the infested tanks. I have a large 2 gallon metal pot that I fill with snail-infected gravel and bake at 450 degrees F for at least an hour. After cooling it down, I use bowls and a kind of panning-for-gold method to pour off the dead snails as they are stirred up in the bowl. This gets rid of the empty shells and is truly effective as long as you have gotten out all the snails and gravel and have not re-infected the tank. I put a large koi in the tank where the gravel was removed for a day or two to get the invisible ones. The downside is that it is a lot of work and if there are a lot of MTS -- do the panning operation before and after cooking or else there will be a serious seafood smell emanating from the oven.

Pond Snails and Ramshorn snails (snails that lay jelly-masses of eggs and have no trapdoors).
You can net out the larger snails and a small koi or comet will eat the small ones and not bother your fish and I have found that the Spixie snail can totally emiminate the egg masses. Spixis (spixie) is a small type of apple snail that lays large masses of eggs underwater or at the surface. A neat feature of Spixies is that they start out life inside these egg masses and eat their way out. Apparently they retain a taste for snail jelly and once you get a few larger spixies they will eat all new egg masses before the snail babies inside can grow up -- making them self limiting -- they will also devour the pond sail eggs as well as ramshorn snail eggs they can get to. Just catch out the larger pond and ramshorn snails and make sure there are no places where the Spixies cannot get to the eggs. When well-fed the spixies will not eat your plants and when you are sure all of the pond/ramshorns are gone just remove the dime-sized spixies and you are done. Apple snails and mystery snails will eat the egg masses of ramshorns but apparently not the eggs of pond snails. One problem with pond snails is that they can lay their eggs above the surface and apparantly some of the eggs will not hatch out for a long time. Frequently a pond snail or two will show up demonstrating some time release survival trick so be sure to watch for these 'sleepers'. Certain cichlids at a certain age will also take out the smaller snails and if you net out the big ones the population of snails can be reduced or eliminated. 3 inch oscars or jack dempseys will do the job but larger oscars will not touch them. Pacus are snail eating machines when they are small. A lot of my systems have a sump with multiple tanks attached and I will put a pacu, an oscar, loach, or a koi in the main sump where the water pump is and let the fish get any snails that end up in the sump due to the water circulation. Just remember to feed the fish enough to keep it alive and hungry but not enough to make him ignore a snail snack. In this case there may be escaped snails in the partitions in the tanks but they will not be re-distributed by the water pump. In my large pond, I expect the koi to eat all of the pond and ramshorns before winter when I can bring in some of the floating plants to try to keep them over the winter without infecting my tanks with pest snails.

Apple snails and mystery/spixies
These I don't consider pests unless I have a planted tank (mystery snails almost never eat plants). The baby snails are fairly small and since they all have trap doors, small koi and comets will not be able to get them. But unlike the pond and ramshorn snails, all of these snails have to get fairly large to breed so can be removed before breeding and the eggs are easily visible for removal if population control is needed. I like to have some apple snails around to eat hair algae that gets going in my greenhouse and a few apples in with my daphnia keeps the bottom stirred and controls the uneaten food problem. All of the apple family can serve as the canary in the coal mine (where the miners took down a canary and if he died they beat a quick retreat from the mine). Apples and mystery snails will be the first animals to die in poor water conditions. They do not have red blood and appear to have very little fat reserve and will quickly die without food. With ammonia, poor oxygen, and low food conditions killing them quickly, an ability to keep them alive should come with a merit badge.

Nerites and assassins
Nerite snails are the hummingbirds of the snail family and their sweet habits (like eating algae but no plants) and beauty should preclude any desire to kill them. If you have extras, advertise the fact and people will come for miles to take your extras. The nerites will lay eggs in fresh water but they will not hatch so overpopulation is not a problem. Also they do not get very large. Assassin snails are also desireable and beautiful -- looking like little bumble-bee striped footballs with snorkles. They stay quite small and apparantly lay one egg at a time and are difficult to propogate even when you would like to get a larger population. Assassins are named because they can kill most of the pest snails but I have not been able to really eliminate a large pest population since they can be breeding up more hoards than the assassins could eliminate. In a large population of MTS, some empty shells will be seen but total elimination is unlikely.

Pond snails on Wikipedia
Here is another A site on freshwater snails
Note that ours are not the ones pictured on the top of this page -- but they sure look neat.

Here are a few of pictures of the Golden Pond Snails:
Golden Pond Snails
Golden Pond Snails. Photo, C. Moormann, 2010 Click to Enlarge

Golden Pond Snails
Golden Pond Snails. Photo, C. Moormann, 2010 Click to Enlarge

Golden Pond with scuds
Golden Pond Snail with scuds. Photo, C. Moormann, 2010 Click to Enlarge

Here are movies of some of the scuds and snails on YouTube on the internet: