Pond Boss® The Block™ 54390 1 lb Bio-Maintenance Puck - The Block™ treats up to 1 acre-foot of water (320,000 gallons). It significantly reduces noxious odors caused by hydrogen sulfide, dead plant material and fish waste. It increases water clarity and is effective over a wide range of pH conditions and water temperatures. For best results, treat every 60 days. Results may vary based on weather conditions and the use of other products