snails in java, what to do

I got two clumps of java moss from a local fish store about 3 weeks ago. Today I noticed that their were snails in the deli cups that I am keeping the moss. Yes it is still in the aquatic form. I picked out the snails, changed the water, and ran water over the moss about 30 minutes ago. What should I do if the problem persists? Will the snails die if I take the moss out of water? Is this moss bad to use?

Thanks, and glad that we are up and running again.