How is duckweed controlled in a pond?

Duckweed is a small floating aquatic plant with many uses in the pond industry. Duckweed grows extremely fast and can double its population in just a few days under ideal circumstances. Duckweed is used as a nutrient control in larger aquaculture applications. The fast-growing plant uses up excess nutrients like nitrogen and phosphorous, thus creating a healthier environment for livestock. They are also a protein-rich plant and make an excellent supplemental diet for aquaculture species such as tilapia and grass carp. Duckweed also has a place in the aquarium industry. They provide shelter for shy species and even provide a means of reproduction for some species. For all these benefits, this small plant species can also quickly become a nuisance to pond owners. It can outgrow a small pond in a matter of weeks or sometimes days. Duckweed blooms can deplete pond oxygen, creating stressful conditions for livestock. Although spread can be quite easy, eradication of a population can be quite difficult.

There are three basic removal methods; Mechanical, Chemical and Biological. Although each has its advantages and disadvantages, the style of each pond will dictate the appropriate method to use. The most common approach is mechanical removal. The most common approach is to simply capture excess plants from the pond. While this can be effective in smaller ponds, it is often tedious or impossible in larger bodies of water. Surface skimming can be a very effective way of removing excess plants. This implies the construction of a surface skimmer as an inlet for the filtration system. The duckweed will flow into the skimmer, preventing an epidemic. The common downside is that duckweed will constantly clog the skimmer. If cleaned regularly, surface skimmers are very efficient in small to medium sized ponds.

Chemical removal can be very effective, but it can also contribute to other problems. Herbicides used to control live plants can be very detrimental to a living ecosystem and should be used sparingly in any natural living environment. In addition to controlling duckweed, these chemicals can also harm more desirable ornamental plants and will severely damage the biological filtration system. This can lead to nuisance algae or even death to livestock.

Biological control may be the safest and easiest to implement. Grass carp and tilapia are two popular options for duckweed control. Tilapia in particular are often farmed with duckweed as a food source. While these fish may be sufficient for long-term control, measures other than this may need to be tried. Natural control is often too slow to control overly large populations, but you may very well be able to keep levels low once duckweed is under control.

Small to medium sized ponds tend to do very well with a combination of surface skimming and biological control, while larger bodies of water may require a more complicated approach. In the end, duckweed, like all other pests, needs to be controlled early. Once an epidemic population is established, it can be very difficult and time consuming to defeat.