FWIW, a simply solution for getting rid of invertebrates is adding copper.
Clowns are definitely nicer to look at though than old pennies sitting on the bottom of the tank. 
Do you find the copper from the pennies leaches into the silicone or just into the water? I know copper-based meds can get absorbed into the seals and then you can't keep inverts in the tank down the line.
I don't really have any evidence to say one way or another. I've used both old pennies (new ones won't work well

) and copper medications, but I've never purposely kept invertebrates. The best I can say is that there was no discoloration in the seals after using it like I've found with some other medications (malachite green for example stains a lot).
FWIW, a simply solution for getting rid of invertebrates is adding copper.
Clowns are definitely nicer to look at though than old pennies sitting on the bottom of the tank. 
Very interesting I've never heard that before. How does the copper affect the snails? doesn't harm the fish though?
I've not found a good answer to this question myself. Every just says "it's toxic!". I did find one allusion to copper being involved in their circular system and a comparison suggesting "too much copper for snails" is similar to how "too much iron is bad for people". Fish and other vertebrates can fall victim to copper poisoning, but due to body mass it takes far more to kill a fish than it does any snails.
One thing to be careful of killing all the snails at once is an ammonia spike when they all suddenly die together. If the tank starts to get cloudy at all a water change is necessary ASAP!
Another thing to be careful of is that some plants are sensitive to copper. Vals are the first that come to mind. Some are tolerant though, of which anubias come to mind.
A final consideration is that copper might kill some good bacteria in your filter. Unless you tank is overstock and not necessarily overfiltered, it's not a huge risk IMO.
For more information than I'm willing to type, this seemed to be a good reference:
http://www.aquaticcommunity.com/snail/coppersnail.phpThe only part I didn't entirely agree with was the suggestion that activated carbon could be used to help remove the copper after treatment. Activated carbon binds with organics, not elements.