Aquatic weeds

Page last updated: Friday, 8 August 2014 - 11:35am

Please note: This content may be out of date and is currently under review.


Controlling aquatic weed infestations poses major challenges. Waterways are environmentally sensitive systems and particular attention is needed when utilising chemicals for control. Consideration for the ecology of the infested area, including the wildlife and fish living in and around the water and other native plant life, will all have an effect on what chemicals you can use. Emergent weeds are often controlled with the use of glyphosate at the prescribed label rates. When treating emergent water weeds the application method should reduce the potential for chemicals to enter the water. Application by “painting” the herbicide directly onto the target weed, with a brush or herbicide blanket, will ensure that the chemical is applied directly to the target weed. This reduces the potential for spray droplets to enter the water.

For larger infestations of free floating and floating leaf aquatic weeds, a range of chemicals can be used, including glyphosate, diquat or 2, 4-D, when the plant is actively growing. Submerged weeds are often the hardest to control. The volume of water needs to be calculated accurately and chemicals applied uniformly to achieve the desired outcome. If the infestation is particularly large consider temporarily removing the water by drainage or pumping. The weed can then be removed manually or treated with a herbicide. After treatment the water can be returned and the waterway restored to its pre-weed status. In a home garden situation the best control available is to manually remove all parts of the plant from the pond or aquarium and burn or freeze them or allow them to dry out completely before putting them into plastic bags and into the bin.

What to do

  • Do not buy aquatic weeds for your garden pond or aquariums. Always ask for native pond species which will also encourage frogs.
  • Dispose of unwanted pond and aquarium plants by drying or freezing them for at least 24 hours before placing in the household bin. Do not compost aquatic weeds as many seeds can withstand drying and freezing. The plants can also be burned or solarised.
  • Avoid buying aquatic weeds from markets and websites where invasive species are possibly being sold. Buy from reputable nurseries and aquarium stores only.
  • Do not take plant cuttings or replants of invasive and declared plants from friends or family, as this will spread weeds further.
  • Never dump aquatic plants, rocks, water or fish from your pond or aquarium into drains or waterways.
  • Control any weed infestations before they spread and become a major problem.
  • Educate yourself and others about aquatic weeds and their impact.

Report banned species to the Pest and Disease Information Service (PaDIS) on 1800 084 881. Photographs can be emailed to for identification.

Please read the sending specimens for identification web article before sending, or taking, samples to the Pest and Disease Information Service, 3 Baron-Hay Court, South Perth, 6151, WA.

Contact information

Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080