Evolution Aqua Pure Aquarium Balls are a bacterial treatment designed for all freshwater tropical aquariums. Each ball contains millions of live bacteria and enzymes that work to break down harmful ammonia and nitrite in your aquarium water, which can be dangerous for fish. These balls also help to decompose organic waste, a common cause of poor water clarity. Regular use reduces the need for filter cleaning and maintenance, and helps to mature and start up filters more quickly. Simply add 1-2 balls per 25 litres of water weekly for maintenance. For initial use or to address clarity issues, add 5-10 balls per 100 litres. Placing the balls in a filter bag within the filter is recommended for optimal results.