try adding a fish that will eat them, in the future whenever you buy live plants rinse them for five or ten minutes under COLD water the snails will become sluggish and fall off the plants as well as the eggs that are on there will lose their adhesion and will fall off into the sink under the water, also if you have a smaller tank i would suggest some aquarium salt, you can raise the gravity a little bit in a fresh watter tank with out causing harm to your tropical fish. botias and loaches are great for eating snails. or if you have a community tank try adding a bolivian ram they have done wonders in my 55 gal as far as cleaning up the snail problem. not only that they are a colorful fish and about the only cichlid you can put in a community tank with out having your other fish disappear.
Hope this helps.