Don't be in a rush to get assissin snails. One thing you can do to help keep hitchhiking snails, snail eggs, and other pests is to rinse your new plants off with H2O2 (hydrogen peroxide) before planting them. Plus assissin snails need snails to feed off of so they would starve in a snail free tank. Another thing is if you add assissin snails you can never add any good snails such as Nerites or Malaysian Trumpet Snails while the assissins are in your tank. Just something to think about.