This easy to use sachet from Fluval can be just dropped into the filter, and should be changed every 2 weeks for optimum performance. This box contains 4 sachets to get you started, with 1 sachet treating up to 60L (can be used with a smaller tank still, and cannot be "overdosed").
This use of chemical filtration ensures that the water conditions are kept at their best, with long lasting cleaner surfaces, meaning your overall maintenance is reduced. It helps to ensure that cloudy water is eliminated, as well as odours and any discolourations. It can be used with any type of filter, and goes along with your regular tank cleaning maintenance.