This article is from the Aquaria: Disease, Algae and Snails FAQ, by Elaine Thompson, Thomas Sasala and George Booth
One of the most beautiful kinds of snails are the Mystery snails.
These snails have a shape similar to the Pond snail, but their spiral
is rounder, and they grow much larger. They can reach tennis-ball size
if well taken care of. The come in many varieties. The snail's body
can be dark, or almost albino (very light with a bright orange speckle
pattern). The shell can be dark, bright orange, albino, or
multi-colored striped (length-wise like the Ramshorn). The Apple snail
variety typically has the multi-colored stripes, with a dark body. In
general these snails don't eat living plants. They prefer algae and
dead plant/animal material (canned spinach will get you a very large
Mystery snail).
 
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