Getting a new fish that you are not 100% sure you want to solve a snail "problem" is idiotic. The chemical treatments kill all inverts in a tank under the water level through a high dose of copper, some fish are copper sensitive aswell but the main harm is you have hundreds of rotting snails releasing an ammonia spike into the water which causes the filter to overload and thus you get dead fishies.
Either embrace the snails or be slow and steady with your eradication method (the best method of eradication is prevention and you should of washed your plants if you didn't want hitchhikers). Embrace them as they will eat excess fish food, keep algae growth minimal, quite beautiful when they become larger and the light speckles through their shells, some species sift through the sand thus turning it and preventing bacteria build up, MTS eat detritus thus minimising the need to gravel vac and they fill ecological niches you would otherwise have to do artificially. To eradicate you should spend a week not feeding your fish, place cucumber in the tank for 2-3 hours with the lights off and remove once the snails are thoroughly chowing down several times a day, do not squash against the glass as this may cause them to release eggs instead pick them off and throw away. After your week long onslaught of consistent physical removal of the snails use a high copper chemical treatment designed to remove pest snails for a week and feed your fish sparingly every 2 days ensuring no waste. Then return the tank to normal light, feeding regime and run carbon in the filter for 2 weeks to remove the excess copper.
