I have all Fluval canisters and 4 on the 220g. I have found cleaning them every month ensures no excess buildup which can increase nitrates over time. On my fluvals I rinse all the sponges under tap water until the water runs clear, change out the filter floss, but never touch the bio-media. I rarely use carbon or Purgen in any of my filters as I find it's not needed in my planted tanks. I even have a Fluval 406 on my 55g nano fish tank that has a very low bio-load even with a lot of fish (due to their tiny size) but still clean that canister monthly. It's a quick and easy clean. I prefer knowing my filters are clean and not contributing to any excess toxin or nutrient levels.