This article is from the Beginning Fishkeeping FAQ, by Thomas Narten with numerous contributions by others.
Snails, like algae, can be both useful and detrimental to a tank. Some
species will burrow in the gravel, aerating it and keeping it from
being compacted; others will eat algae. However, some species will
reproduce unchecked, destroying plants and generally being an eyesore.
You can protect against snails by sanitizing anything inanimate you
add to your tank in a 1:20 bleach solution, and treating new live
plants in potassium permangenate or Alum. For ridding your tank of
snails, you have little recourse other than vacuuming as many up as
possible, though clown loaches are rumored to eat snails. The SNAIL
SECTION of the DISEASE FAQ describes individual species of snails and
specific remedies.
 
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