Preventing didymo and other Freshwater pests in our waterways

Published Thu 15 Feb 2024

Check, Clean, Dry: preventing didymo and other pests.

Dragon Boaters rely heavily on having good water for our fun and racing. We have to behave as guardians of the water health.

Freshwater Biosecurity Advocates from Environment Canterbury are at our Aoraki Open, on Lake Ruger on Sunday 18 February 2024 to help us understand the risks, and what we can do about it. 

Freshwater pests can be spread by your activities in and around waterways. If you've been in a lake, river, stream or wetland and plan to move to another within 48 hours, you must clean all your gear that has been wet using the 'Check, Clean, Dry' method. Here's how to do it (see more):

Clean your gear when moving between waterways

Invasive freshwater pests, including didymo, could squeeze the life out of our country's most precious rivers and lakes. They can be spread by a single drop of water or plant fragment or single fish egg. You can help to protect your favourite waterways if you always check, clean, then dry any equipment that comes into contact with the water, between every waterway, every time.


Remove any plant matter from your gear and leave it at the site (the river or lake bank), or put it in the rubbish. Don't wash plant material down any drain.


Use 10% dishwashing detergent mixed with water and leave the item wet for 10 minutes.

The rule of thumb for 10% detergent mix is:

  • for a 500ml (large) spray bottle, put in 3 tablespoons
  • for a 10-litre bucket, put in 1 litre of detergent.

Cleaning large volumes of gear

If you have large amounts of gear (for example if you have a fishing or diving business), you can find other suitable options in Appendix 3 of Check, Clean, Dry: Information for sporting event organisers.

'Check, Clean, Dry' for sporting event organisers [PDF, 2.6 MB]

Make sure you:

  • follow the manufacturer's safety instructions for any cleaning products
  • choose a method that won't damage your gear
  • check the cleaning mix has penetrated right through the item before you soak it for the recommended time
  • check eCan cleaning instructions for Cleaning specific items – some have different cleaning requirements.

Treatment by drying

Ensure your gear is completely dry to touch, inside and out, then leave dry for at least another 48 hours before you use it (didymo can survive for months on moist gear).

Drying can be used as stand-alone treatment for non-absorbent items if you take great care to:

  • make sure gear is completely dry to touch, inside and out
  • leave dry for at least another 48 hours (after drying), before entering a different waterway.