Chuck,

Duckweed is difficult to control. Period. We've been successful in controlling duckweed using a fluridone product such as Sonar. Depending on your geographical location, tilapia are successful at controlling duckweeed, also.

A diquat product such as Reward should be used as only a temporary cure. If using diquat, it's important to mix a 3/4% solution of a chealated copper such as Cutrine Plus in order to have more success controlling duckweed. Don't forget to add a non-ionic surfactant to your mix, also!

Duckweed is an indicator of a higher than normal phosphate concentration in your pond. Make sure you are managing your watershed as well as possible to prevent any additional nutrient loading.

Aeration systems can be helpful for encouraging aerobic microbe activity therefore processing nutrients more efficiently. Aeration, however, will not cure your duckweed problem. We have a municipal client with a 3.5 acre pond. It has two 5 HP fountain aerators and was covered shoreline-to-shoreline in duckweed and watermeal last summer. We're treating it with Sonar this spring and stocking tilapia to help control the duckweed throughout the season this year.

Hope this helps!