(the featured image is an EPA photo showing an algal bloom)

Keep yourself, and your animals safe!

I found some strands of algae in my rainwater pool – water that is 40 degrees cold!   I had thought that this algae would only grow in warmer water. Think again.

I realized that my dogs can drink out of this pool, and the toxins stay in the water, after the algae dies.  Killing the algae can make it worse.  The algae dies, but the toxins remain.   Mycrocystins, the liver toxin, have a very long ‘half-life’  (‘half-life’ is the amount of time that passes till the toxin level falls to half the original level).  The half-life for mycrocystin is said to be 3 weeks.

So, what to do next? Keep reading to find what I learned about blue green algae and how it can affect our health, and the health of all our animals.

The link below is from VCA Hospitals, and talks about the effect of cyanotoxins (toxins from blue green algae, also called cyano bacter), and something about treatment.  Algal toxins can cause symptoms almost immediately and death can soon follow.  There are two major types of toxin or concern, hepatic (liver) and neuro (brain).  Read the article below to find what VCA recommends.   I now keep activated charcoal capsules or tablets on hand, both for my animals, and for myself. People can be poisoned too, by swimming, drinking water, getting water on the eyes, walking barefoot on a contaminated beach, and by eating certain seafoods.

Here is an article which explains effects on pets

Not only can we also die from a single exposure, but long term dietary exposure seems to be implicated in ALS, Parkinson’s and Alzheimer’s diseases.   Dr. Michael Greger tells us more…

YOUR safety and seafood!

And this one… 


EPA gives lots of useful information and tells us what we can do.

  • Report blue green algae blooms
  • Keep out of it
  • Don’t eat filter feeding seafood, don’t eat in contaminated areas – like air that smells of toxins/algae
  • Don’t go in the water if there are sign posted that the water is unsafe – even if it looks great
  • Beautiful looking water can be deadly.  Once the algae is gone, the toxins persist
  • We cannot tell by looking whether blue green algae is producing toxins – or not.  However, if the air smells bad, LEAVE
  • Be careful about even walking on the beach barefoot, if you know that there have been blooms there.

Information from EPA


I needed to know what I should do about my pool.  What happened to the toxins if I treated the algae with an algaecide or Chlorine?  The answer:  nothing, except that when the blue green algae, or ‘cyanobacter’ dies, it releases all of its toxins into the water.  Depending on the type of toxin, it can take months and months for the levels to lower significantly.  So, water can look great, and be deadly.  The laboratory tests are expensive – around $300 where I found them.  And, most test only for the hepatotoxins, like ‘mycrocystin’.  Neuro toxins are also deadly, but they reduce by half within three days.

Very sobering to me was that the pools/tanks/waterers where my animals drink can be toxic, at some level or another.  I am working on a plan for managing this actively from here on out.  Post in the comments below if you are interested in what I come up with.  For one thing, I will be dumping the pool water away from where we walk barefoot.

And, if you want information on toxin half lives – read this

Although blue green algae can be very toxic, we cannot tell, by looking,  if a blue green algae bloom is producing toxins.  However, there is a simple test that can tell if the bloom is regular green algae or blue green algae.  This pdf explains how:

But this problem is increasing.  Rather than test for it, what can we do to prevent it?  Learn more about this below:

What causes a harmful algal bloom?

And, are there any new tests that are not expensive, and fast enough to use to test water to swim in, or allow our animals to be in?  Fortunately, yes!  But it won’t be ready for about two years.  Read more below.  Rah, rah Finland!

15 min test from Finland, coming in 2 years






Larry Sonntag set the following two photos:  In the first, the algae near the waters edge is horse hair, very safe, but the light brown scum is Anabaena, potentially toxic. It can occur without the horse hair being present. Or it can be mixed together, so if someone lifts a clump up and it sticks together that doesn’t guarantee there isn’t toxic bacteria present.  The second photo shows mainly horse hair, which is safe, but in the center is a fluorescent patch which can be toxic.  That part can have many colors and not always bright ones.  I believe its called Oscillatoria. I can’t find a picture but one other type I’ve had looks like little black clumps.  All these samples were tested by the Wisconsin DNR a couple of years ago.