What Do I Do if My Pool Has Turned Green?


The sun is shining. The skies are blue, the birds are chirping, and your swimming pool is a lovely hue of — green!?

How did things go this horribly wrong?

Well, your lovely swimming pool can turn green overnight if the circumstances are right. All it takes is some algae, a lack of chlorine, and an especially warm day.

It’s not easy keeping your swimming pool sparkling clean.

This article will illustrate why swimming pools can turn green and what you can do to return them to their sparkling, transparent hue once again.

Why is My Swimming Pool Green?

Pool water needs to be tightly regulated all the time.

A green discoloration in your pool often has the same familiar culprits:

  • Excessive algae, pollen, or metals in the water.
  • Not enough chlorine.

Finish things off with a nice steamy weather to bring everything to a boil.

Lack of maintenance accelerates the bad conditions needed to make pool waters cloudy green, and murky.

Let’s look at each factor in detail.

1. Excessive Algae

Algae is insidious. It grows incredibly fast if undefended against. Come summertime, when the mercury levels in your thermometer rises, algae thrive. Warm conditions are essential for any kind of bacterial growth, after all.

The lack of a swimming pool cover can expose your pool waters to the full blast of the sun’s rays. This can make your fibreglass swimming pool surprisingly warm and facilitate the perfect conditions for algae growth.

Algae gives your pool water a forest green hue. In the early stages, algae make your pool look cloudy and dull. Algae give rise to ammonia and always occurs in conditions of

  • High chloramine levels
  • Low cyanuric acid levels
  • Low free chlorine levels
  • High chlorine demand

Which brings us to the next factor.

2. Not Enough Chlorine

Chlorine is your strongest line of defense against unwanted bacterial growth in pool water. Lack of maintenance can easily result in effectively low chlorine levels. This makes your pool susceptible to mosquitoes, insects, and algae bloom.

Un-chlorinated water quickly turns swampy and is unsafe to swim in.

3. Excessive Pollen

Nearby, greenery such as plants and trees give rise to pollen. Pollen is a tiny substance, caught only by fine pool filters and is carried by the wind. As pollen builds up, it forms a solid shape and appears mustard green on the water. Green discoloration caused by pollen is fortunately safe for most people, but can cause serious problems for those with allergies.

Certain breeds of flora around your pool give rise to pollen faster than other breeds as well. This makes it important to carefully select the plants around your pool.


4. Excessive Metals

Copper ions give rise to clear-looking green water. Metals such as copper are introduced from various sources such as cheap algaecides and acidic water. Even the internal components of your pool such as the copper heater elements can contribute.

Whenever you shock your pool water, the metals within oxide and cause the water to turn green.

This discoloration can be permanent and can stain the surfaces of your pool.

5. Turning Green Into Blue

Your first solution is shock treatment.

Use an algaecide supplement and shock your pool with chlorine to stop the problem in its tracks.

If your water turns a darker color, it might be too late and you will have to call in professionals to drain your pool.

But as long as the water is simply cloudy green, then a shock of chlorine is needed. Bring the free chlorine level in your pool water to the correct level of 3 pp for non-saltwater pools and 3-4 ppm for saltwater pools.

The best way to induce chlorine shock is through liquid chlorine that uses Sodium hypochlorite.

Algae have a slimy coating that acts as a protective agent against chlorine. Algaecides penetrate this protective layer and allow the chlorine to finish off the algae.

You can brush the entire pool as well to physically break down the algae into smaller pieces so that your algaecide can work more effectively.

Check your chlorine levels constantly as your pool pump works its magic. Every time the chlorine level dips, add more.

6. Pollen Begone

A makeshift skimmer basket with a sock can snatch up the finer pollen particles in the water. Pool filters and slime bags aren’t an efficient solution. You’ll need to go through several socks at least. Flocculants act quickly to bring the pollen into clumps and make them settle at the bottom of the pool. Add a dash of flocculant to your pool skimmer and skim away. Let the pump run as you do so. Then switch off the pump and rest for 12 hours or so. This should allow the sediments to settle on the bottom of the pool to make for easy cleaning.

7. Copperfielding your Copper

Sequestrants bring metal particles together to allow your filter to easily sort them out. Once you use a sequestrant, use a chemical cleaner to backwash the metals from your filter. Understand how the metals got into the water in the first place to prevent the buildup from ever happening again.

Rust from your pool components can cause copper buildup, so take measures to improve the alkalinity of your pool. Continue using sequestrants on a weekly basis to thoroughly clean your pool on a regular basis.

The Bottom Line

A green pool is mostly a symptom of an improper cleaning schedule. Chlorine, algae, and pollen are the most common causes of pool discoloration and a regular cleaning schedule can keep this problem at bay.

Don’t be impatient once you’ve taken all the measures needed to return your pool to a cool blue. There will be a lingering cloudiness until you’ve let the filters finish their job and return your pool to a clean, sparkling blue once again.

Regularly test your pool’s pH levels, chlorine levels, and even hire a professional servicing company if needed. An ounce of preventive maintenance is worth a pound of problem solving. Have a regular schedule in place to prevent your pool from being taken out of action.