One of the best ways to ensure clean healthy pond water is to grow large numbers of pond plants. Pond plants will feed on the nutrients in the pond water, especially if the pond has fish that produce waste. Pond plants can either be submerged under water or float on the water's surface. Adding pond plants to your pond can allow you to create your own naturally balanced ecosystem that would require minimal maintenance and little to no artificial filtration.
Line a mesh basket container with sacking (coarse cloth) to help keep the soil in the container once it's in the pond.
Fill the basket halfway with aquatic soil. Position the plant in the centre of the basket. Make sure you hold the plant by the stems and not the delicate roots, which could be harmed.
Add soil until it is an inch from the top of the basket. Add pebbles to the top of the container to keep the soil from floating away and from curious fish that could bother it. Water the container to pack down the soil.
Thread a piece of string through one of the holes in the mesh container. Hold both ends of string in your hand, and slowly lower the container until it's about 18 inches under the water's surface. Let one end of the string go, while still holding the other end, and let the plant settle to the bottom of the pond.
Remove your floating pond plants from the nursery bag. Place them in a shady part of your pond so they can rehydrate their leaves before they go back in the sun.
Make a fence around your plant--so it will not float to sunny parts of the pond--by taking an old hula hoop, anchoring it with a large fishing weight or rock, and placing your plants inside the hoop.
Remove the hula hoop after the plants have had a few days in the shade, and let your plants float where they may. If your pond does not have shady spots to protect your new plant, you can place the plant in a container with pond water in the shade for a few days. Change the pond water in the container every day.
Move non-tropical plants to the deepest part of your pond during the winter. Bring your tropical plants indoors for the winter until the pond temperature is at least 18.3 degrees C. Submerged plants will feed through their roots and foliage and give off oxygen for fish to breathe. Floating plants are effective filter plants that simply float on the surface of the pond.
Check with your local aquatic nursery before purchasing submerged or floating plants. Some plants are illegal in some states because they could upset ecosystems.