Kills mosquito larvae. Completely non-toxic to animals such as fish, birds, wildlife and pets. Each dunk will last up to 30 days in standing water and will cover 100 square feet of surface. Safe to use in pet watering bowls, horse troughs,lakes, bird baths, fish ponds, flower pots, aquatic gardens, flood control basins, unused swimming pools and other areas where standing water is a possible breeding ground for mosquitoes.