Aqueon PURE is nitrifying live bacteria that helps to maintain a well-balanced aquarium and is easy to dose. Nitrifying bacteria live on surfaces such as filter media, d?cor and gravel, converting harmful ammonia and nitrite to less toxic nitrate. By dosing weekly, the enzymes and bacteria breakdown excess waste from over feeding or detritus in the aquarium which can help reduce filter maintenance. The unique sphere design of PURE provides surfaces for the bacteria and enzymes to reside until conditions are ideal to be utilized efficiently. This "time release" style means PURE cannot be overdosed and any excess bacteria will be waiting until needed. PURE disappears to the eye when added directly to the aquarium and works most effectively when introduced to a filtered tank system. While it does not dissolve completely, the small PURE left behind will go unnoticed and can be removed during water changes. Aqueon PURE is the solution for aquarists who want to bring balance to their aquarium with the convenience of simple dosing and a blend of bacteria plus enzymes that breakdown excess waste. This does not replace water changes but provides a sort of safety net should the habitat become unbalanced. Satisfaction Guarantee. Easy to dose gel ball. Live beneficial bacteria that breaks down harmful waste. Cannot be overdosed. Helps maintain clear water. Safe for all freshwater aquariums. Add one PURE per 10 gallons of tank water each week.. Add two PURE per 10 gallons of tank water when starting a new aquarium. Easy to dose gel ball. Live beneficial bacteria that breaks down harmful waste. Cannot be overdosed. Helps maintain clear water. Safe for all freshwater aquariums.