Pond plants can help to keep your pond clean by adding oxygen, preventing algae growth and removing carbon dioxide, phosphates and ammonia from the water. Even the death of pond plants is beneficial in that the biodegrading portions of the plant provide food for organisms who then become food for your fish. Just be sure you use fish-friendly plants if you have fish in your pond. Potting pond plants is only slightly different from potting land plants. By following a handful of steps, you can have your own pond-cleaning plants in no time.
Fill the bottom of two pots with a layer of aquatic plant fertiliser. Be sure the fertiliser you use is safe for fish if you plan on adding fish to your pond.
Add top soil to the pots. Refrain from using potting soil or peat moss, as these potting agents tend to be too light and will float to the surface.
Place a submergent elodea plant into the pot and cover with more top soil. Elodea is an underwater plant which is often used as an oxygenator, as it helps to remove carbon dioxide from the water and keep the water clear. Be sure to add small rocks over the soil. The rocks work in two ways: first by adding weight to the pots to keep them from floating to the surface, second by keeping the fish in your pond from nibbling at the soil.
Place an emergent plant like frogbit, a pond plant whose leaves emerge from the water, into the next pot. Frogbit works to remove ammonia and phosphates from pond water. Place a little more soil around the plant. Be sure you add rocks around the top of the pot, as you did with the elodea plant.
Plant a few free-floating varieties of water hyacinth and water lettuce. Planting free-floating plants is simple: merely place them in the pond and watch them grow. Water hyacinth and water lettuce help to remove ammonia and phosphates from pond water, thus providing a stable environment for more sensitive pond plants to grow. Since they compete for oxygen and sunlight with algae on the surface, they also help to keep the algae population down. Studies done by NASA in 1975 at the John C. Stennis Space Center found that water hyacinth works so well in removing impurities from water that it is now being considered for use in water treatment facilities.