You Can Lead Your Horse To Water…

Summertime Algae in your horses drinking water? A trip to Rural King (or your closest farm supply store) and the purchase of a barley straw treatment named Stock Tank Secret might make your water trough maintenance a lot easier!


It’s been hot.  Very hot. Summer came early this year, and so did all the issues that intense heat brings, including algae – an aquatic plant that grows in water from organics that make their way into the tank, whether it is blown in by wind or introduced from your horses’ saliva.  

It takes no time for the hot sun to change your clear and clean water to that familiar emerald green sea of floating slime. Those of you who own horses and are responsible for their needs are familiar with cleaning water troughs – and during a Florida summer, it is, at the very least, a weekly chore. While the type of algae found in livestock tanks and troughs is not toxic, it could hinder your horse’s ability to drink deep.

When I was young and riding at a local barn, the owners had goldfish in a huge water tank that wet the whistles of at least 15 horses. The goldfish inhabited the trough to keep the algae to a minimum. One day I was standing close by when a black and white Shetland pony named Comanche stopped for a drink.  He was genuinely thirsty and drinking deeply when his head suddenly flew up; his eyes looked like they would pop out of his head.  

A goldfish, the size of my hand, was flapping in his mouth; the tail protruded on one side of the pony’s mouth and the head on the opposite side!  I had a good laugh, but I am sure the goldfish and Comanche weren’t nearly so amused. 

So when I heard about putting barley straw in a watering trough or tank to keep algae at bay, I was skeptical.  Straw in a trough? How could that be? 

When I researched this method, I learned that barley straw placed in the water begins to decay. No question there.  However, during the decaying process, it produces a chemical called Lignin, which causes the algae to die. 


In laymans terms, Lignin is a chemical found in the walls of plants that lend structure. According to, it is a complex polymer of monolignols (which are aromatic alcohols). It is insoluble in water and alcohol, but soluble in weakly alkaline solutions. It is the second most abundant organic polymer on Earth (behind cellulose, another plant component) and makes up about 30% of non-fossilized organic carbon. Some scientists are touting Lignin as a possible fossil fuel replacement in the future!

Most important to us and our horses, though: lignin is non-toxic and perhaps a better alternative to using chlorine bleach, which is what I have used in the past to scrub my water tanks.

I made a trip to my local Rural King and purchased Stock Tank Secret, a barley straw product made just for keeping tanks and troughs clean, for under $6.  The product description claims it will maintain small tanks algae free for up to two months. So after thoroughly cleaning the trough with bleach and refilling the automatic waterer, I dropped the bag of barley straw into the water, and waited to see what would develop.  (Or, ideally, not develop.)

Usually, by the end of the first week, the water is slimy.  With Stock Tank Secret, at the end of the second week, the water was clear, and the slight green film I initially saw in week one was gone as well!

The Stock Tank Secret package states that it will last up to two months, and that you may need two for larger stock tanks. My small water tank began to produce the familiar green hue by the end of one month, yet no apparent strands were floating in the water. 

Still, it is a vast improvement over my previous maintenance methods, and I will be rebuying Stock Tank Secret.  When the weather is hot, I’ll take all the help I can get to make sure my horses get the cool, clean drink of water they need as much as their humans do!

To find the store closest to you or order online, visit!

Barb currently resides in Central Florida with her three horses; when she’s not writing or riding for HRL, she loves to read and travel.

Posted in