As long as you get it out, bleach is perfectly safe. Especially for nuking the snails that have taken over in a previously established tank XD
I use 1 cup of bleach for every 10 gallons... That should be plenty to kill anything in the tank (and burn your hands if you dont rinse them after touching the water).
Just remember, bleach can hide everywhere. Multiple water changes and gravel vacuumings should happen after you are ready to remove the bleach.
Just because there is always a chance, I do not take responsibility if you do not get it out of your tank and it kills your fish... :lol: