Pond filters UV can guarantee clear water in even the brightest conditions. Most filters are now made with a pond filter uv built in to the lid of the filter to control green water caused by algae. The media in all filters cannot filter out the single celled algae that cause green water because the algae is small enough to pass straight through the foam. The action of the UV part of the filter causes the algae to clump together so that the foam filter them out of the water.
We recommend replacing the lamp in your pond filter uv on a regular basis for maximum efficiency.