i take my baskets of bio media out and rinse in tank water during a water change every 3-6 months. and my mechanical filtration every 3 months or so but it depends on the fish and type/size of filter used. for example using an eheim 2217 on a 4ft tank, not overstocked, filled with guppies and corydoras would need cleaned every year or possibly 2 years as they are not messy fish.