the cerith-shaped one is a malaysian trumpet snail (Melanoides
tuberculata) if they resemble this photo:
http://www.applesnail.net/content/photographs/non-apple/melanoides_tuberculata.jpg
the other ones are called ramshorn snails (planorbis sp.). here's a
photo:
http://www.applesnail.net/content/photographs/non-apple/planorbis_spec_1.jpg
both should not eat plants.
--
Steve
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