Blue-Green Algae and Dogs in NSW: How to Check Before a Swim
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Quick answer: before your dog swims in a river, lake, lagoon or dam in summer, check for blue-green algae alerts. In NSW, WaterNSW publishes alerts (via its Water Insights site or 1800 999 457), and local councils share them too. On a red alert, keep your dog out of the water completely. Avoid any water that looks green, scummy or smells musty. If your dog swims in or drinks suspect water, rinse them with clean water and call your vet straight away.
What is blue-green algae?
Blue-green algae (cyanobacteria) occur naturally in fresh and brackish water. WaterNSW explains they can multiply quickly in still or slow-flowing water with plenty of sunlight and nutrients, which is why blooms are more common in warm, calm weather. Some types produce toxins that can be harmful to people and animals.
What do the alert levels mean?
NSW uses three alert levels for recreational water, based on national guidelines and published in WaterNSW and council algae reports:
| Alert | What it means | For your dog |
|---|---|---|
| Red | Bloom conditions. Water may look green or discoloured with scums or clumps. Algae may be toxic to humans and animals. | Keep your dog away. WaterNSW reports say owners should keep dogs away from high alert areas. |
| Amber | Algae may be multiplying; water may have a green tinge and musty smell. Levels can rise to red quickly in warm, calm weather. | Be cautious. Safest to skip the swim. |
| Green | Algae present at low, natural levels. | Normal caution. |
A red alert can sit on one stretch of river while the next is clear, so check the specific site.
How to spot a bloom yourself
- Green, blue-green or brown discoloured water
- Paint-like scum on the surface or along the edges
- Greenish clumps through the water
- A musty or earthy smell
If it looks or smells wrong, keep your dog out, even if there's no alert yet. Wind can push scum into the shallows where dogs drink and paddle.
Why are dogs at risk?
Dogs swim through scum, drink the water and lick their wet coats afterwards. If the algae are producing toxins, that can make a dog seriously ill quickly.
What to do if your dog swam in suspect water
- Get your dog out and stop them drinking or licking their coat.
- Rinse them thoroughly with clean water, wearing gloves if you can.
- Call your vet or emergency vet straight away, even if they seem fine.
- Watch for signs such as vomiting, diarrhoea, drooling, weakness, wobbliness, trouble breathing or seizures, and go to a vet immediately if you see any.
Where to check alerts in NSW
- WaterNSW: algae alerts via Water Insights, or call 1800 999 457.
- Your local council: many councils post local algae updates for lakes and lagoons.
- Signs on site: look for warning signs at access points.
- For coastal lagoons and estuaries, also check Beachwatch for water quality after rain.
Safer summer swims
- Bring fresh drinking water so your dog doesn't drink from the lake or river.
- Choose flowing, clear water over still, warm shallows.
- Rinse your dog after every freshwater swim.
- Saltwater beaches have their own risks. See pufferfish poisoning and is salt water bad for dogs?
FAQs
Is blue-green algae always toxic?
Not always, but you can't tell by looking. Treat any bloom as dangerous.
Can I boil water from a red alert area for my dog?
No. Boiling does not remove algal toxins, according to NSW algae warnings. Bring your own water.
Does blue-green algae happen in the ocean?
Alerts mostly cover rivers, lakes, dams and some lagoons and estuaries. Check local alerts for coastal lagoons.
Out exploring rivers and lakes this summer? Keep an AirTag on your dog's collar in a Pawfetchers waterproof holder, rated to 1 metre for 30 minutes (AirTag sold separately).
Sources
- Wentworth Shire Council: Blue-green algae updates (WaterNSW alert definitions)
- Federation Council: Blue-green algae red alert warning
General information only, not veterinary advice. If you're worried about your dog, contact a vet.
