Rosewood Pure Aquarium is specifically for use in freshwater aquariums to help achieve crystal clear and healthy water and reduce filter maintenance. The beneficial bacteria and enzymes held within each “gel like” ball breaks down Ammonia and Nitrite whilst cleaning up organic waste when added to new or existing filters. It is recommended to use 1 or 2 balls per 25 litres of water on a weekly basis. A single tub, containing 50 balls, will typically last four months when used in a 60 litre aquarium.