Hugo Water Cleanser helps to make filters work more efficiently by using microbes that eat organic waste faster while using less oxygen than bacteria. Why use Hugo Water cleanser? Less water changes, reduced filter cleaning, healthier fish with less infection, more enjoyment- less stress. Simply wash the water cleanser ball & place into your filter. Suitable for aquariums sized 1-1000 litres. For internal filters: Place the balls into the bottom of the sponge compartment. For canister or hang on filters: Place the balls into the filter.1 ball = 11grams & should keep a tank up to 125 litres clear for 3 months.