Keep pond water fresh and crystal clear the way nature does, with the cleansing power of beneficial bacteria and enzymes. This discreet dispenser submerses in your pond, and releases a 100% natural water clarifier 24 hours a day for a full month. It breaks down organic matter that clouds water, reduces excess nutrients and prevents mineral buildup. Non-toxic — safe for fish, pets, aquatic plants Cleans ponds from 300 to 2,500 gallons for 30 days Includes retrieval line to make refilling easy Refills available separately; set of 4 is a 120-day supply For really large ponds–up to 225,000 gallons–use the Aquaspheres All-natural, beneficial bacteria Plastic dispenser is 3-5/8" dia x 2-3/4" H Cleans ponds from 300 to 2,500 gals for 30 days Made in USA To calculate pond gallons: Length (in feet) x width x average depth x 7.5 = gallons.