Pura Phoslock is the benchmark ferric hydroxide media for total phosphate removal in all aquaria. Fast acting, long lasting and very effective in reef, marine, planted and delicate freshwater aquaria. It is the product of choice for many critical water purity applications. Stable and will not disintegrate even if subjected to high flow rates. It permanently and irreversibly binds phosphate and silicates. With regular use of PhosLock any aquarium fresh or salt, reef or planted, will stay much cleaner and less maintenance labor intensive. It does not contaminate water with free iron. Removes large quantities of phosphate, arsenic, silicates and other heavy metals and thus greatly reduces propagation of algae. No impact on trace elements and desirable fertilizers like potassium. Convenient to implement. Media bag with PhosLock can be placed inside of canister filters, power filters, pond filters, sumps, refugiums, corner filters, next to uplift tube on UG filter plate. It can be placed directly into Bio-Bags or other fine floss bags. It is 5 to 10 times more effective than white activated alumina media and it is completely safe for fish and invertebrate, fresh and salt-water aquariums. This 1135-gram Phoslock comes with 6-inch by 12-inch 300-micron media bag. Treats 2500-gallon aquarium.