Healthy Ponds 52450 Refills for All Purpose Pond & Water Cleaner 2,500; 4 30-Day Refills Treat up to 2,500 Gallons for 120 Days Keeps small ponds and water features (backyard ponds, fountains, etc.) Up to 2,500 gallons clean, clear and free of green organic growth Unique patented time-release system delivers a proprietary blend of naturally occurring bacteria and enzymes into the water for 30 days Veterinarian approved and safe for fish, plants, birds, animals and humans Results may vary; over time bacteria and enzymes will work to reduce organic debris, improving water quality and clarity while eliminating odor 4 30-day refills; treats up to 2,500 gallons for 120 days