In future, check new plants before putting them in a tank. You can dip them, using a solution of bleach/water, or hydrogen peroxide/water, or Excel/water, and it will kill algae as well. With some plants, like anubias, with harder leaves and not too many of them, you can run them through your fingers and feel if there are any egg clutches. If so, they are easy to squeeze off gently. I usually just let them dry thoroughly and toss them in the trash, but burning them is not a bad idea.
I also have shrimp in all my tanks, so when I see a nuisance snail, like a bladder snail, I just crush it. Shrimp really enjoy snacking on dead snails, so they are soon eaten and thus disposed of, and it's a good protein boost for the shrimp too.
If you can't find Assassin snails, another species called Asolene spixi snails are an option. A member of the Apple snail family, they are attractive and usually don't get much bigger than a full grown Zebra nerite. With random dark stripes on pale shells & ivory coloured bodies, they eat most other snails, including each other, so their population never gets out of hand. They won't kill every nuisance snail but they sure keep the numbers down.
