All chlorine is toxic if used incorrectly. Pool store "Liquid Shock" is either Ultra Bleach (6%) or double strength (12%). Same stuff. Be sure to use regular or ultra unscented, non-sudsing, non-gel, ordinary bleach. Generic/store brand is fine. Both the pool store and the bleach companies sell a solution of sodium hypchlorite and brine (salt water). Used as directed, it's as safe as any other chlorination...safer, too, than some.