Last Updated: 4/12/12

Pros and Cons of Snails
Prevention of Adding Snails with Live Plants
Snail-Eating Fish
Killing Snails

Good Things About Snails:

• Some species eat algae.
  
• They will clean up leftover fish foods.
  
• They will eat dead plant and animal materials, thus cleaning the tank.
  
• They may burrow through the substrate and aerate it (mostly just trumpet snails do this).
  
• They do not harm live, mobile fish.
  
• They are interesting in their own right and part of the ecosystem. Snails are ubiquitous to ponds.

Bad Things About Snails:

• Some species may eat plants.
  
• If they multiply too rapidly, they could die off. Their corpses would be a major pollutant and could poison other animals in the tank or pond.
  
• Large snails can create copious amounts of waste adding to the nutrient load.
  
• Snails may eat fish eggs or newborn fry.
  
• Some specimens may harbor parasites and other ailments which could be passed on to fish.

By soaking live plants before adding them to a tank, fewer snails will end up in the tank or pond. I used to treat all my plants to kill snails but ended up with snails anyway. Here are the methods to treat live plants. Never add these chemicals to an aquarium (except potassium permanganate is used as a medication at much lower doses). Treat the plants in a bucket or tub.

Note that for ponds, even if you never add a single snail or snail egg, wild animals can and will bring them to the pond. So, why fight it?

• Potassium permanganate - soak for 10 to 20 minutes in a 15 ppm solution (ppm = milligrams per liter; 15 ppm = about 0.4 Tablespoons per gallon water) or for a day in a 5-10 ppm solution.
  
• Alum - soak for 2 to 3 days in a solution of about 5 teaspoons of USP Alum (aluminum sulfate) in a gallon of water. Plants may begin to suffer without light during such a long soak. This may not kill snail eggs. Pete suggests soaking for just 3 to 5 minutes (concentration unknown).
  
• Bleach - soak for 2 to 10 minutes in a dilute bleach solution (about 1 part bleach to 20 parts water), then soak for 20 minutes in fresh water with a high concentration of dechlorinator. This may damage sensitive plants but bleach is the easiest of the chemicals to obtain. Bleach also kills algae. Various species of plants are more sensitive than others and cannot tolerate this more intense treatment. Anacharis and hornwort specifically may fall apart and not recover.

Fish that eat snails are called malacophages. Most of these fish eat snails by crushing them in the back of their throats but puffers and some cichlids use their jaws and labryrinth fish (bettas, paradise fish, and gouramis) pull the snails out of their shells.

The following fish will eat squashed snails:

• Most fish!

The following fish will eat appetizing snails like pond snails:

• Goldfish, koi, and orfe
  
• Most loaches
  
• Most labryrinth fish
  
• Any really hungry fish!

The following fish may eat snails in general if there is nothing better to eat:

• Clown and skunk loaches (Botiamacracantha and horae)
  
• Puffers (Tetraodon species; will attack other species of fish)
  
• Banjo and Asian Bumblebee catfish
  
• Some cichlids: Malawi, African butterfly, Thomas', Chocolate, Convict, Keyhole, Angelfish, Apistogrammas, and some other cichlids
  
• Giant gourami (too big for most tanks)
  
• Paradise fish
  
• Opaline, blue, or three spot gouramis (may not eat snails)
  
• Betta or Siamese fighting fish (may attack other fish)
  
• Black ghost knifefish

Sometimes small species of snails end up in aquariums or ponds when they are not wanted. They can breed into large colonies. Often, reducing the amount of food going into the system will keep their numbers in check. In ponds, goldfish, koi, and orfe may eat small snails such as the pond snail. In aquariums, certain loaches like the clown loach will eat small snails. Most fish will eat snails if their shells are broken open. See above for a list of fish purported to eat snails.

The simplest way to reduce snail numbers is to pick them out of the tank or pond by hand. Then, they can be broken for the fish to eat or thrown away.

Because most snail-killing chemicals also harm live plants and other invertebrates, they should be avoided. Also, when the snails die, there could be a large ammonia and nitrite spike due to all the decomposing bodies. In a fish-only tank or pond without sensitive fish, perhaps the chemicals could be used. The most common chemical used to kill snails is copper sulfate. It was sold as "Had-a-snail." Copper sulfate will kill all invertebrates including mollusks, crustaceans, and insect larvae.

Snails can be baited using the foods mentioned under feeding (lettuce and algae wafers are good baits). A few hours after the lights go out, remove the food which should be covered with snails.

For information on treating live plants, fake plants, and ornaments to rid them of snails before adding them to the tank or later, see my algae page.

As a last ditch effort, an aquarium can be torn down. See here for information on the steps to follow to disinfect everything. When doing this, remove all living animals and plants so they do not die. Instead of bleaching everything, one aquarist suggests adding straight ammonia (sold as a cleaner, be sure there are no extra ingredients) to read a level of about 50 ppm (using a test kit). Add it daily for about a week. Then, do a number of major or total water changes to reduce the ammonia, nitrite, and nitrate down to low levels. In this manner, you can kill most living things in the tank without killing off all the good bacteria. This aquarist used it to kill snails and planaria which are flatworms. Remember, never do this with animals or plants that you want to survive still in the tank.

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