duckweed on a pond

Asked June 14, 2014, 3:43 PM EDT

Our pond is covered with duckweed, I am using a pool skimmer to lift it out. Is there something else we can do or use on it without harming the environment?

Ogemaw County Michigan pond and water gardens

3 Responses

Hello,Thank you for using eXtension for your pond question. Using a pool skimmer to manage duckweed sounds like a pretty creative solution to your problem. Using an aerator or pond fountain can help to clear the center of the pond as these plants are floating and easily moved about. This can make scooping them out an easier task as well once the duckweed is pushed to the edges. Some fish will feed on them. Stocking your pond with fish can also help if your pond is deep enough to sustain them. Koi and goldfish will feed on duckweed but not extensively, it is not recommended that you use grass carp as they are weak feeders on duckweed. Here are some websites that might help you:, Additionally, shading the heavier infested areas with black plastic can kill the weeds in that section. Tie floats onto the edges of a sheet of black plastic and place over an area of your pond for 10 to 14 days moving the plastic to new areas as needed.

So where can we find Koi and are the goldfish you are talking about just the ones you can buy anywhere?

Hi, you pose an interesting question because the correct answer is it depends. Purists will say only from an approved breeder, others who aren't so fussy will suggest any pet store that sells fish. I know that koi for example are priced by breeding, size and age, etc. Gold fish can also command high prices if you want the fancy ones of any size. However, if you are willing to give it a try - I personally have had success with the regular run of the mill Department Store (Meijer) gold fish and koi. Calculate maximum fish capacity based on your pond size. But you can start with a minimum number of your choosing and add more if needed. You may need to invest in a few additional items though to get started: A pump fountain or filter if you do not have an inlet and outlet stream for your pond - a kettle pond; as your fish grow larger a heron decoy to ward off predators. Heron need a 50ft radius to feed so won't land near another one. If you start with the real little ones (fry size) get more than minimum as they take time to grow and fall prey to many things in the pond. The size of your pond determines the volume of fish stocked and don’t forget they will breed if conditions are good. Also plan to supplement their food this way you can also train your fancy fish to come to the surface for viewing. No feeding in the winter, they start to go into a sort of stupor when the water gets below 40F. Here are some websites that offers advice for hobby fish grower. NOTE that I am not endorsing any product or business but there are not a lot of extension materials for goldfish ponds so I look to industry and organizations for good information. This one is from England: About the fish: How to calculate how many fish to put in your pond: Managing Michigan ponds for sport fishing: (this is for sport fishing but the principle is the same for hobby fish) Pond management guide pdf: