How to Cultivate Duckweed

Duckweed is a nutritious food supplement for herbivorous and omnivorous fish. It also provides a breeding ground for beneficial bacteria and microorganisms. Duckweed is a simple plant that does not require much light or care beyond occasional thinning. Cultivation techniques can easily be incorporated into an existing aquarium set up. Food production for fish may require a dedicated set up exclusively for growing duckweed.

Things You'll Need

  • Container or aquarium
  • Treated water
  • Light (optional)
  • Air pump
  • Vinyl air tubing
  • Airstone
  • Check valve
  • Duckweed start
  • Fish (optional)
  • Fertilizer
  • Brine shrimp net
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Instructions

  1. Setting Up

    • 1

      Select a place that will be relatively undisturbed by drafts from windows, doors and heating vents, but receives bright, indirect light from a window. Add a small fluorescent light above the growing container, if needed.

    • 2

      Fill the container with water that has been treated with dechlorination chemicals, or aged. You can also use rainwater, R/O water or distilled water that is mixed with 50-percent treated tap water.

    • 3

      Connect the air pump outlet to one end of the vinyl tubing and the airstone on the other. Somewhere on the line towards the pump end, install the check valve in-line to prevent water backflow into the pump. Place the airstone in the water and turn on the pump to oxygenate it and create circulation.

    • 4

      Add a starter sample of duckweed and let it float around. Eventually, any upturned leaves will correct their position to absorb the light and the plants will float to the edges of the container.

    • 5

      Add fish to provide organic fertilizer for the duckweed, if desired. Make sure the type of fish you select do not eat duckweed. Add the fish slowly over several weeks and keep the stock levels low.

    Maintenence and Harvest

    • 6

      Change at least 25 percent of the water once a week and replace it with fresh, treated water.

    • 7

      Fertilize once or twice a week using a commercial aquarium plant fertilizer. Use less fertilizer than recommended if there are fish in the container.

    • 8

      Harvest the duckweed periodically when it needs to be thinned out or for feeding fish by skimming it off the surface with a brine shrimp net.