I have a lot of snails and I'm wondering if they're good or bad for plants.
There are two kinds:  ones that are kinda brown upto about a cm in length and
the shell is a spiral, cone shape.  These look like pretty ordinary type snails
and don't reproduce as often as the other ones.  They are small, 1mm -3mm in
size, semi-transparent shells in a spiral, disk shape.  I can't observe any
obvious damage to the plants but I'm not sure.  Does anybody know the names of
these snails?  Sometimes I find a fairly substantial egg cluster on the top or
bottom of a leaf.  I think they mostly eat algae.  Are they good or bad?  Are
snail species competitive?  Can some kinds compete with more beneficial types
and even kill them off?

 - Steve