Phyllanthus fluitans is an annual that grows in hardiness zones 9 to 11. It grows on the surface of the water and needs full sun. In areas with cool winters, you can bring it indoors and grow it in an aquarium under good light.
You can plant sagittaria in the mud on the edge of a body of water, or place it in a special pot that is submerged. Sagittaria self-seeds, so it is important to deadhead it if you do not want too many plants.
Winterize hardy water lilies by cleaning away dead material, removing the plants from the water and protecting them in plastic bags.