Aqueon PURE is an easy to dose nitrifying bacteria supplement to maintain a well-balanced aquarium. Nitrifying bacteria live on surfaces such as filter media, dÃ©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 idea to be utilized efficiently. This â€œtime releaseâ€ style means PURE cannot be overdosed and any excess bacteria will be waiting until needed.