Wait for a very windy day, as this is when the duckweed plants are naturally pushed to the pond edges.
Use a long-handled, fine mesh net to collect and remove the duckweed from the edges. You can also use a swimming pool net with a long handle.
Repeat the process regularly to keep the plants from multiplying. Remove as many of the plants as you can during each removal process.
Buy koi from a fish store to introduce into the pond as a preventative strategy for duckweed.
Choose koi that have little color since these are less expensive. The dull color of these fish makes them less valuable in the koi industry.
Use at least 50 koi for every acre of pond, as recommended by the Ohio State University Extension.
Aerate your pond regularly since duckweed thrives in stagnant and undisturbed waters. Pond aeration kits are available at garden supply stores.