A controlled population of snails is not harmful, and can even benefit an aquarium by helping to remove waste material, prevent substrate from becoming polluted by agitating gravel, and keeping surfaces free from algae. Many people keep the large apple snail in aquariums with fish to add a bit of extra interest, and most aquarium stores will sell these snails, which are easy to keep and do not normally breed excessively. Other snail species can become a pest if they begin to multiply, which they can do very quickly under the right conditions, making the aquarium look unsightly and clogging filters and pipe work.
Snails are normally introduced into an aquarium as eggs or adults on live plants, décor moved from other tanks, or occasionally accidentally scooped up and transported with fish. Checking all live plants thoroughly for snails and eggs, or dipping plants in a snail killer solution before use can help to delay introduction, but it is likely that even the most vigilant fish keeper will at some point find snails in their tank. A well-maintained aquarium that is not overfed has nothing to fear from a few snails. Rather than prevent the introduction of snails it is best to accept their presence and if they become a problem, take it as a sign that their may be other problems with the aquarium which need looking at.
The biggest cause of all snail problems is overfeeding; snails will thrive on leftover particles of food in the substrate and breed rapidly if there is plenty of food available. Feeding should be the first check you make if snails become a problem, and if this is the cause adjust your feeding amounts accordingly and carry out a thorough clean of the substrate using a gravel cleaner. A build-up of general waste matter in the substrate will encourage snails so gravel cleaning should be used as a standard method to keep snail populations low in any case. Snails will also thrive on algae, so introducing a good selection of algae eating fish will help to remove their food source.
Snails are often involved in the transfer of diseases amongst fish populations since they act as a carrier for parasites and disease pathogens. Diseases transferred by snails usually occur in natural environments however, and in the majority of cases, snails introduced into the aquarium originate from disease free environments and are not a cause for concern. Since snails are most commonly introduced as eggs on live plants, the newly hatched snails carry no diseases so will not pose a health risk to your fish
Snail killer treatments are readily available at all retailers, but should only be used as a last resort if natural methods have failed, since these treatments have a number of drawbacks. The biggest problem with using these chemicals is that if they do work, your aquarium will be filled with lots of dead snails, which will pollute the aquarium, causing health problems and resulting in unsightly bacterial blooms. Most treatments will never kill all the snails, and may not affect eggs, so newly hatched snails and surviving adults will continue to breed, and will also have lots of available food in the form of the snails which were killed. If you do use a snail treatment, check the instructions carefully, since some can be toxic to sensitive fish species such as loaches, and avoid using water conditioners during treatment, since these can neutralise the metal compounds in the snail killer treatments.
Snail traps can be purchased, although it is equally as effective to make your own. There are various methods of doing this but the two most popular are to sink a lettuce leaf, or place a food item such as a sinking wafer under an upturned saucer, on the bottom of the tank overnight, and in the morning you will find the saucer or lettuce leaf covered with snails, which can be easily removed. If the attentions of fishes prevent the traps from working effectively, a good method I have used is to place a food item inside a water bottle filled with tank water and pierced in several places with holes big enough for snails but too small for fish - in the morning you will have a bottle filled with snails for easy removal. If you use a lettuce leaf, or other vegetable as bait, pouring boiling water over it first will kill and soften the leaf, making it more attractive to snails
Most scavenging fish will eat snails as part of their natural diet, and are a great way to keep populations low. It should be noted that if the tank were overfed, snail-eating species would probably not bother with the hassle of hunting and eating snails. Good snail eaters for smaller tanks include Dwarf Chain Loaches, Zebra Loaches, and Corydoras sp. catfish. Larger tanks can accommodate some of the best snail eaters including Clown Loaches, Pictus Catfish, and Synodontis sp. catfish. Freshwater pufferfish are also excellent snail eaters, although they may not mix with many community fish. Some gouramies will also eat snails by sucking them out of their shells. To aid the snail eating species, pieces of décor such as bogwood should be regularly turned over, exposing the snails and eggs, which are usually underneath. You can also kill snail eggs and make them more attractive as food by removing objects with eggs attached, pouring boiling water over them and then returning the item to the aquarium.
The Assassin Snail, Antentome helena also known as the Beast or Killer snail, is an attractive little trumpet-style snail which feeds on other snails and has a slower reproductive rate than most 'pest' snails. Adding a few assassin snails to your tank will help to reduce the population of other pest snails, and eventually may even eradicate pest snails. The Assassin snails will grow to around 1.5-2cm and have a colourful shell, making them an attractive addition, and once they have eaten all other snails in sight, they will scavenge amongst the substrate for waste material. Whilst they do not reproduce as quick as other snails, they can still produce numerous offspring, but at least if this does happen they have value and can be sold on or given away to other fish keepers or your retailer.
Quite the opposite in fact, snails are scavengers and will clean up debris whilst helping to maintain a healthy substrate and also eat unsightly algae. This myth probably arises because snails thrive in aquariums that are overfed, and partially polluted through other means, such as lack of correct maintenance. In addition, when fed large amounts of vegetable mater, some snails can cause a slight clouding of water by the release of micro organisms used to aid digestion, although this is rare and easily controlled.
Snails are excellent scavengers and will devour any suitable source of food. When a fish has recently died or is close to death and unable to move, snails will very quickly home in on this tasty meal. The aquarist may see their fish lying on the bottom being eaten by snails, either dead or showing hardly any movement, but the snails are not the cause of death. A bit of common sense should be enough to realise that a healthy fish with normal swimming ability has nothing to fear from a slow moving snail.
Some snails, including common varieties found in garden ponds, will damage delicate plants, but in the vast majority of cases snails will not cause any significant damage to aquarium plants. Snails are grazers and have tiny mouths more suited to eating non-fibrous algae. Healthy plant leaves have thick protective surfaces, which are very difficult for snails to break through. This myth is easily explained however, since snails will relish dead, damaged, or dying leaves so are often seen eating plants which are already deteriorating, and being spotted at the scene of the crime, are immediately given the misplaced blame. Discuss Snails and Invertebrates.