This filter for the Haliburton/Muskoka should be changed every 4 - 6 months (depending on usage). When inserting filter into the Muskoka/Haliburton skimmer basket ensure that the side with the hole is facing downwards to allow proper filtration. This filter replaces the old blue foam variety and fits in the old skimmer basket by removing the white hard plastic tray on the bottom of your skimmer basket. By changing the filter from foam to cartridge Canadian Spa has increased the filtration ability of its portable models giving you crystal clear water for longer. For more effective filtration please clean filter every few weeks using the filter clean chemical which can be found on the Canadian Spa Company Website. Also we recommend the Canadian Spa Company Filter Cleaning Tool for getting inbetween the folds of the paper whilst cleaning, as the Cleaning Tool's teeth are specially designed for easier and faster filter cleaning.