Question
Tiny snails ate all my water lilies last year. We tried to treat them and almost killed all our fish.  Is there something that will kill the snails and not fish?  We are over loaded again with these pest. Thanks for any suggestions.

Answer
Well, as you found out, chemicals used to kill snails also kill other animals.  They usually use copper which is toxic to snails, algae, some plants, delicate fish, and basically all the invertebrates and even bacteria in the pond (not good for the nitrogen cycle!).  There are two basic options.  The first is manual removal.  In a large pond, this is basically impossible unless you have countless hours to pick off snails and wipe off their eggs.  The other option is to introduce predators.  Some fish like orfe and even goldfish will eat snails.  Most of the good snail-eating animals are tropical and won't work in a pond.  Raccoons love snails but I doubt you want them in messing with your pond like mine do!  Another option is to add more plants to the pond.  You can put in more plants snails prefer to eat like submerged plants (anacharis and horwort come to mind).  The fish will also eat those.  Some years, snails dessimate my waterlilies too but other years they don't.  I just let nature hammer it out.

Good luck!