Dangerous Waters Ahead! Keep Your Pets and Family Safe

Article by Lauren Sandrin


Many of us have seen the news stories lately about dogs dying after what seems like a routine swim in Colorado’s many watering holes. What could be killing our best friends after a fun day out? The answer is surprisingly simple: bacteria. Specifically, blue-green algae (aka: cyanobacteria) is responsible for the growing number of pet deaths and it can affect humans as well!

Cyanobacteria flourishes in warm, nutrient-rich water which is common in the late summer months. The bacteria reproduce quickly and floats to the surface of the water, creating large floating “mats” of material that clings to the edges of bodies of water. Not all cyanobacteria produce the toxins responsible for causing illness or death, but there is no way to tell without extensive testing if one particular clump of algae is safe versus another. The only way to keep your animals, children, and yourselves safe is to completely avoid water that is known to be contaminated, is a “pea soup” color, has algae clumps around the shore, or looks like blue or green paint was spilled in the water. 

Symptoms of algae toxicity in animals are the following: vomiting, diarrhea, bloody/black/tarry stools, jaundice, seizures, coma, difficulty breathing, death. Unfortunately, there is no antidote for algae toxicity and vet care is limited to primarily comfort care and euthanasia. Death from algae toxicity can occur within hours of exposure and after immense suffering. 

While absolutely not foolproof, there are at-home tests you can use to get an idea of the presence of cyanobacteria in a water source. Again, this is not to be used to determine safety but it is an excellent science experiment to do at home!

Jar Test

If your lake or pond water appears very green, the jar test can help determine if the color is from blue-green algae, or just an overabundance of more beneficial types of planktonic algae. Gather the following materials: A clear jar (pint to quart size) with a screw-top lid, such as a canning jar or pickle jar with the label removed, and a set of rubber or latex gloves.


  1. With the gloves on, collect a sample just below the surface of the water (avoid collecting just the top layer of scum).
  2. Fill the jar about three-quarters full. Do not fill the jar completely; algae give off gases that may cause pressure build-up in the jar which could break it.
  3. Wipe any scum off the outside of the jar and screw the lid on.
  4. Put the jar in the refrigerator and leave it undisturbed overnight.
  5. Carefully remove the jar from the refrigerator and see where the algae has accumulated. (Do not shake or agitate the jar at all or the algae will mix into the water again and negate your test results.)
  6. If the algae are settled out near the bottom of the jar, it is likely that your lake does not have a lot of blue green algae.
  7. If the algae have formed a green ring at the top of the water, there is a strong possibility that your lake does have a blue-green algae community.


Stick Test

If your lake or pond has a mat of green material floating on the surface, the stick test can help determine what it is. Gather the following materials: Sturdy stick that is long enough to reach into the water without getting algae on your hands, and rubber or latex gloves


  1. With the gloves on, push the stick into the surface mat and slowly lift it out of the water.

  2. If the stick comes out looking like it has been dipped into a can of paint, the material is likely blue-green algae.

  3. If the stick comes out with green strands like hair or threads, the material is probably filamentous green algae, which may be a nuisance but is not a health hazard.

The stick test can fail when a type of blue-green algae called Lyngbya wollei is present. This species can form tough filamentous mats that float to the surface, similar to mats formed by harmless filamentous algae. But Lyngbya wollei algae differentiate themselves with a putrid sewage-like odor and by sometimes releasing purple pigment in the water around them. (Courtesy of the Minnesota Pollution Control Agency) 

Some alternatives to swimming in lakes, ponds, or streams are available for our furry friends! Canine Rehabilitation and Conditioning Group in Englewood offers an indoor pool and swimming lessons for dogs, as well as free-swim sessions. Jasper’s Splash Zone in the Springs is a great location to learn how to dock dive, and is perfect for dogs that love to retrieve or fetch! Finally, a cheap kiddie pool in your backyard can offer a chance to splash and cool off, just be sure to empty the pool after use! (Bonus: Dump it in the yard for some deep watering of the lawn!)



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