The number of fish and plants you plan to have determines the filter size
Knowing the volume of your pond is the first step towards water gardening success. Knowing the fish and plants you intend or more importantly foresee having in your pond in a couple of years time is equally important. Bear in mind both plants and fish grow and multiply!
For simplicity we have broken down the selection to 3 types. What category of pond yours falls into determines the maximum pond size each ClariTec filter is capable of handling efficiently with acceptable maintenance. More fish means higher load on the filter, and less plants covering the surface means more algae growth, all of which determines if you need a bigger filter to handle it. Choose which scenario is closest to your pond and then you can read what size of pond each filter is suitable for. Using a filter on a larger than recommended pond means more maintenance is required and the filter may struggle to cope with the waste load.