Aquatic weeds are plants that are in the wrong place, many are plants that have been introduced from overseas from the aquarium or ornamental trade, agriculture or accidental spread.

Unfortunately, weeds thrive in Wet Tropics conditions which makes our waterways particularly vulnerable when plants escape from ponds and aquariums. The first records of aquatic weeds in the Wet Tropics show that they began to arrive in the 1800s.

Most of the ones we are dealing with today were introduced through the aquarium trade, as culinary plants or released for agriculture. The internet has made it worse by causing an explosion in food plants being imported from other parts of the world, especially south-east Asia.

In other parts of Australia, weeds die back during the dry months but because we have so much water all year round, weeds continue to spread.

Why are aquatic weeds a problem?

• They smother native vegetation, reducing biodiversity.
• They alter water quality by depleting oxygen and blocking sunlight.
• They create breeding grounds for pests like mosquitoes.
• They create favourable habitat for other aquatic pests like the pest fish, Tilapia.
• They impede water flow, attract sediment, and alter channels, increasing flood risks.
• They obstruct recreational activities and water infrastructure.
• They threaten agriculture by invading drains, irrigation systems and crops.

What are some of the most problematic aquatic weeds in the Wet Tropics? 

• Amazon frogbit
• Pond apple
• Water hyacinth
• Water lettuce
• Water mimosa
• Cabomba
• Bog moss
• Hygrophilia
• Limnocharis
• Olive Hymenachne
• Paragrass
• Aleman grass
• Salvinia

What can aquarium lovers do?

• Know the legislation and which plants are on the ‘naughty’ list.
  
• Buy aquarium plants from reputable suppliers.
• Look for local alternatives.
• Dispose of aquarium contents responsibly

What has been done to tackle aquatic weeds so far?

Unfortunately, aquatic weeds are almost impossible to eradicate once they’ve been introduced. The best we can do is control infestations as they crop up by removing weeds manually or with the use of herbicides.

Community groups, rangers and parks services are among those involved in weed control programs. We can all help by making sure we don’t inadvertently transfer weeds to other areas on machinery and boats.

To find out more:

DOWNLOAD factsheet on aquatic weeds in the Wet Tropics