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Tanwax Lake closed because of toxic algae

On July 30, we closed Tanwax Lake out of an abundance of caution. Algae are highly visible across the lake, but the water doesn’t currently have elevated levels of toxic algae—which we would normally use to determine a lake closure. We took this extra precaution because of the lake’s high recreational use.

The closure advisory means you should stay out of the water. High levels of toxic algae increase risk of illness, especially to children and pets. The lake is unsafe for people and pets. Signs are posted at the lake to let you know about the advisory.

When you see algae, don’t swim, wade, waterski, or fish. As wind direction changes, the algae could move elsewhere in the lake. When in doubt, stay out!

We will inspect the lake again next week. If the bloom is no longer there, we will leave the advisory in place for 2 weeks out of an abundance of caution. Find our list of current surface water advisories at

What are toxic algae?
Toxic algae, also known as cyanobacteria, occur naturally in lakes. They can produce toxins that make people, pets, and other animals sick. Read our brochure to learn more about toxic algae.

How can you spot toxic algae?
Toxic algae can form a scum layer and look like green pea soup. They can also look streaky, be dispersed in the water column, or form clumps. Algae can have different colors, most often green but also brown, red, and blueish. Wind and weather conditions can change the amount and location of algae.

What are the symptoms?

Muscle weakness.

See your medical provider if you may have been in water with toxic algae and have any of these symptoms. Small children are at most risk since they have small bodies and are likely to ingest water.

Skin in contact with toxic algae can become irritated or break out in a rash. This is different from Swimmer’s Itch.

How can toxic algae affect my pets?
Pets are at great risk. They have small bodies and are more likely to ingest larger amounts of toxic algae. They may drink water with toxic algae and lick their fur. Take your pet to the vet when it shows any of these symptoms.

Difficulty breathing.
General weakness.

What should I do if exposed to toxic algae?
You can get sick within minutes to hours of exposure. Rinse off anyone or any pets exposed to toxic algae immediately. Look for signs of illness and seek medical treatment if symptoms occur. For exposed pets, prevent them from licking their fur to groom.

Can I eat fish from toxic algae contaminated water?
Avoid eating fish from areas with visible algae. Always clean fish well and discard guts.

What should I do if I see an algae bloom?

Don’t drink lake water.
Don’t swim or waterski in areas with visible algae.

Keep pets and livestock away.

When in doubt stay out!

What causes toxic algae?
Toxic algae need light, the right temperature, and nutrients. You can help to reduce nutrients and prevent toxic algae:

Reduce your use of fertilizer.
Maintain your septic system.
Put pet waste into the trash.

Questions? Contact the Surface Water Program at (253) 649-1420 or or visit to learn more.

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