Phoslock is a professional strength phosphate remover. Phoslock is a ferric hydroxide media which will completely remove phosphate from all aquariums. PhosLock permanently binds phosphates. and with regular use of any aquarium, fresh or salt, reef or planted, will stay cleaner longer and be less maintenance labor intensive.Simply place a media bag with PhosLock inside of: canister filters, power filters, pond filters, sumps, refugiums, corner filters, next to uplift tubes on undergravel filters. PhosLock can be placed directly into Bio-Bags or any other fine floss bags. 5 to 10 times more effective than white activated alumina media and it is completely safe for all fish and invertebrates, fresh and salt-water aquariums. 1135 gram size will treat 2500 gallons.