It starts with one or two tiny hitchhikers on a new plant, and before you know it, the glass is covered in dozens of small, moving dots. Bladder snails, ramshorns, and Malaysian trumpet snails are the most common 'pest' varieties that find their way into home aquaria.
A snail explosion is almost always a symptom of an underlying issue: an abundance of food. If you are overfeeding your fish or if there is a lot of decaying plant matter and algae in the tank, the snail population will boom to match the available resources.
If you want to reduce numbers quickly without using chemicals, manual removal is the way to go. One of the oldest tricks in the hobby is the lettuce trap. Simply weigh down a leaf of blanched lettuce or a slice of cucumber at the bottom of the tank before you turn off the lights.
In the morning, the leaf will likely be covered in snails. Gently lift the leaf out of the water and dispose of them. Repeating this for several nights in a row can significantly thin out the population while you work on the root cause.
Nature has its own ways of keeping snail populations in check. The Assassin Snail (Clea helena) is a popular choice because it specifically hunts and eats other snails. They breed much slower than pest snails and are generally safe for fish and larger ornamental snails.
Certain fish species are also famous snail-eaters. Loaches, such as the Yo-Yo Loach or Zebra Loach, are efficient hunters. However, always research the requirements of these fish first; for example, Clown Loaches grow far too large for the average community tank and should not be bought just for snail control.
You can remove as many snails as you like, but they will return if the environment stays the same. To keep them away, start by being more disciplined with feeding. Any food that hits the substrate and stays there for more than a few minutes is fuel for the snail population.
Regular maintenance is equally important. Use a gravel vacuum to remove detritus from the substrate and trim away dying plant leaves before they rot. By reducing the available 'trash' in the tank, you essentially starve the snails out.
The easiest way to get rid of aquarium snails is to never let them in. Most snails enter as eggs or tiny juveniles on live plants. To prevent this, consider giving new plants a 'dip' before adding them to your display tank.
A quick soak in an alum solution or a very diluted bleach solution can kill off eggs and adults. Alternatively, buying 'tissue culture' plants ensures they are grown in a sterile lab environment and are 100% snail-free from the start.
No, they don't harm fish directly. In small numbers, they actually help by eating algae and leftover food. They only become a 'pest' when their population gets out of control and they become an eyesore.
It is generally discouraged. Copper is toxic to many invertebrates, including shrimp, and it can stay in your substrate for a long time. Furthermore, killing a mass of snails at once can cause a massive ammonia spike as they decay.
Generally, no. Assassin snails are much slower than healthy dwarf shrimp. While they might scavenge a dead or very sick shrimp, they rarely catch healthy ones.