This 4-inch sphere is preloaded with a natural bacteria and enzyme blend which reduces excess nutrients, sludge and ammonia, resulting in improved water quality and clarity. A patented timed-release system incubates and releases beneficial bacteria and enzymes 24 hours a day, 7-day a week, over a 30-day period. Each sphere treats up to 1,000-gallon (to calculate pond volume in-gallon, multiply pond length x width x average depth x 7.5). Being all-natural, you can"t overtreat. PRO formula works effectively in water from 34-degree to 110-degreeF. Ideal for stock tanks, koi ponds and small ponds. Safe for humans, pets, fish and plants. Made from a corn-based polymer; after 30-day, sphere can be disposed of or composted. Replace every 30-day. May require 4-6 weeks to achieve water quality improvement. Most effective in ponds with pH level between 6.0 and 8.5. Includes string for easy retrieval. Made in USA.