A combination of filtering plants is the best choice for natural pools. Plants in your regeneration zone withdraw nutrients that harmful pathogens require, and allow beneficial microbes to grow. They will also naturally aerate the water. You'll want several different kinds of aquatic plants in order for your regeneration zone to thrive. Consider planting water lillies, reeds, pond or duckweed, etc. to create a varied and healthy ecosystem.
Take inspiration from your local lakes and ponds! Whatever thrives nearby your home will be much more likely to thrive in your conditions.
