Among the infiltrators of your fish tank - parasites, fungi and algae - are snails. With eggs that are often too tiny to see on the stems of plants or carried on fish, they will establish themselves quickly and spread throughout the tank. Add a snail-eating fish or two. Clown loaches or cichlids have the reputation for eating snails. So do gouramis. Although the cichlids need some special conditions, the other two are good community fish. Clown loaches are especially good scavengers, eating food that falls to the bottom of the tank where they spend their time as well as the snails.
The most common of these snails is the pond snail. While it appears to be relatively harmless and can help rid you of algae and other tank detritus, it can also nibble your plants to death. When their population explodes, your tank can look like a snail farm rather than an aquarium.
While aquarium shops sell snail control solutions, this should not be the first step you take to get rid of them. Unless you can pick them out as they fall dead from the chemical treatment, you will end up with rotting snails at the bottom of the tank, which will quickly foul the water.
Three Steps to Eradicate Snails
Your other fish can eat the snails only if the snail's shell is crushed. You can do this by hand if you want, although it can be very tedious and if you're feeding your fish regularly, they'll take the fish flakes before the snails.
Remove snails by hand or with a long pair of tweezers. Try to do this before the infestation gets out of control. Also try to remove the tiny snail eggs from the plants. If you have only a couple of plants, you can remove them and wash the snails off and replace the plants.
Baiting the snails may also work. Place a leaf of lettuce on the bottom of the tank and the snails will climb on. Remove the leaf and replace it until you've removed a good number of the snails.
The best thing to do is to combine all of the above approaches in order to gain control of the problem. If the snails remain a problem then try a chemical agent. Snails are yet another reason to quarantine plants and fish before placing them into the aquarium.