Green Pool Water That's Not Algae - What Is It?

Green Pool Water That's Not Algae - What Is It?

Green pool water can be frustrating to treat, especially when most remedies focus on removing algae. But what if you have green pool water that is not caused by algae?

In this article we will discuss the causes of green pool water that are not related to algae, ways you can determine the source of your problem, and how to fix green pool water that is not caused by algae.

Causes Of Green Pool Water Besides Algae

Green pool water that is not caused by algae is typically due to dissolved metals in the water. The metal that most often causes a green colour is copper, but other dissolved minerals and metals can sometimes appear green as well depending on your water’s conditions.

Water begins to appear green and leave behind stains once a certain concentration of minerals has been met in the water.

Green stains or green pool water from copper are especially likely to develop after the use of chlorine shock products, as these accelerate the oxidation rate of the metal particles.

Copper in pool water can come from the water you use to fill your pool, and this is especially likely if your pool is fed with bore water.

Another common source of copper in pool water is copper-containing algaecides. While these are highly effective at reducing algae in your water, when combined with shock treatments they can produce metal discoloration and stains.

How To Fix Your Green Pool

Rule Out Algae

Before taking steps to treat issues caused by dissolved metals in your pool, it is necessary to entirely rule out the presence of algae. If you are looking for non-algae based solutions, you are likely fairly confident already, but this test is very easy to perform.

The easiest way to rule out algae in a pool is to check chlorine levels regularly. In a pool with an active bacterial or algal infestation, chlorine levels will diminish faster than normal as the sanitizer works to kill microorganisms.

If your chlorine level is not around zero or at least dropping more quickly, it is unlikely that you have an algae problem.

Test For Metals

This step is not necessary, as most treatment options that work to fix metal discoloration work on all types of dissolved metals, but many pool owners like having the option available to more precisely determine what the cause is.

In some cases, it is possible to get your pool water tested for dissolved minerals and metals.

This type of test is typically not available for at-home use, but many pool maintenance and pool supply stores offer water-testing services that can detect these elements.

This option can be especially useful if you have not been using copper-containing algaecides and suspect that your pool’s source water may be naturally high in minerals and metals.

Remove Dissolved Metals From Your Water

In order to remove the dissolved metals from your water that are causing the green discoloration, you will need to use a metal removing solution.

These products contain chemicals that are known as sequestering agents, which work to keep dissolved metals from dropping out of the solution that is your pool water.

Metal removers prevent stains and water discoloration, but do not remove stains that have already accumulated on the lining of your pool.

To use a metal removing solution, always follow the instructions provided on your product’s packaging.

Most metal removers require that you measure out the correct dose of product, pre-mix the product in a bucket of your pool’s water, and then distribute the contents of this bucket into the deep end of your pool while the pump is running.

After adding a metal remover, run your pump for 24 hours continuously or as otherwise indicated by your product’s instructions. Metal removers cause the pH and alkalinity of your pool to drop after use.

When correcting these levels after treatment, it is important to raise them using very small doses of product to avoid causing stains in your pool.

Treat Stains On Pool Surfaces

You may notice that green patches or stains are on the surfaces of your pool rather than in the water itself. These are formed when the metals in your pool’s water oxidise and become attached to the walls of your pool in unsightly colours.

To treat metal stains on your pool, you will want to use a stain remover. These products are added to your pool while the pump is shut off and are typically left to dissolve stains for a 24 hour period.

Because these products also work on dissolved metals in the water, it is not necessary to use both a metal remover and a stain remover. If you notice stains on the surfaces of your pool, it is fine to begin treatment with a stain remover instead.


Green pool water is unsightly and off putting. Even when it is not caused by algae, it tends to have an unsanitary appearance that can make even the most avid swimmers hesitant.

Luckily, green pools that are caused by dissolved minerals or metals in the water are not too difficult to treat.

With the use of metal removing solutions like sequestering agents and stronger options such as stain removers, you can rid your pool of the green appearance that is caused by oxidising copper and other metals.

Do you have any questions about green pool water not caused by algae? Let us know, we’d love to help!

Louis from Pool Advisor


A chemical engineer by trade, Louis is committed to debunking myths in the pool industry by explaining the underlying chemistry and making it accessible to all.