Is This Water Safe for My Dog? A Pup Parent's Guide to Blue-Green Algae

For water-loving dogs, a lake day is the best day. It's also the one day a year many pup parents never think about until something goes wrong. Here's the plain-English version of what vets want you to know.

What is blue-green algae?

It isn't really algae. It's bacteria called cyanobacteria that grows fast in warm, still, nutrient-rich water, usually in late summer. Some blooms make toxins. Others don't. The only way to know is a lab test, which is why local advisories matter.

Why is it so dangerous for dogs?

Dogs get a bigger dose than people do. They swim with their mouths open, drink lake water, roll in mats on the shore, and then lick their fur clean. Two main toxins do the damage:

• Microcystins attack the liver.
• Anatoxins attack the nervous system and can kill within hours.

There is no antidote. Fast, aggressive vet care gives the best chance. Read the AAHA overview of blue-green algae risks for pets.

What does toxic algae look like?

Watch for any of these and keep your dog out:

• Green, blue-green, brown or red film on the surface
• Water that looks like spilled paint or pea soup
• Floating or shoreline mats, which can be dark brown or black
• Foam, scum or a rotten smell
• Dead fish nearby

Clear water can still carry toxins, especially after a bloom breaks up. When in doubt, stay out.

What are the symptoms of algae poisoning in dogs?

What should I do if my dog swam in algae?

1. Get your dog out and stop the licking. Wear gloves if you have them.
2. Rinse with clean, fresh water, the whole coat and paws.
3. Call your vet or the nearest emergency vet now and say "possible blue-green algae exposure." Don't wait for symptoms.
4. If you can't reach a vet: call the ASPCA Animal Poison Control Center at (888) 426-4435 or Pet Poison Helpline at (855) 764-7661. Fees may apply.
5. Report it to your city or state health department so other dogs stay safe.

How do I check water before my dog swims?

Our three-step habit for every water day:

1. Check the advisory. Search "[your city or lake] algae advisory." Austin, for example, posts updates on the City of Austin algae page (https://www.austintexas.gov/watershed-protection/algae-austins-waterways).
2. Look at the water. Moving, clear water beats still, warm coves. No film, mats or smell.
3. Pack the rinse kit. A gallon of fresh water, a towel, and your own drinking water so your dog isn't thirsty enough to gulp the lake.

In the RuffRuff app, add "water access" notes to a park's amenity updates. When a local advisory goes out, post it in your neighborhood group so other pup parents see it fast.

Frequently Asked Questions

Can dogs swim in lakes in summer?

Yes, when there's no advisory and the water looks clear and moving. Late summer is peak bloom season, so check every time.

Can blue-green algae hurt my dog even if they didn't drink it?

Yes. Dogs swallow it when they lick their fur after a swim.

Are fenced dog parks with splash pads safer?

Treated, regularly cleaned water features don't grow cyanobacteria the way still lakes and ponds do, which makes them a lower-risk summer option.

Is Lady Bird Lake safe for dogs?

It depends on the day. Toxic algae has appeared there repeatedly since 2019, including near Red Bud Isle in June 2026. Check the city's page before each visit.

This post is general information, not veterinary advice. In an emergency, call your vet.