It is essential that you clean your Spa filter/ filters at least once every two weeks. More often if the Spa is heavily used.
Remove your Spa filter and place in a solution of Filter Cartridge Cleaner overnight. Rinse the filter thoroughly and allow it to dry. When the filter is completely dry, clean with a soft brush before replacing
It is worth considering purchasing spare filter/ filters. This will enable you to clean your Spa Filters without interrupting the Spa filtration cycle.