Why Is My Pool Green & How to Fix It: A Comprehensive Guide

by Celestial Solar | Aug 15, 2023

Are you struggling with your swimming pool turning green? Have you ever wondered why it turns green and what you can do about it?


The answer lies in understanding what causes this change. From various types of algae making themselves at home to imbalances in your pool’s chemicals, there are several explanations for green pool water. The solution to clearing green pool water is also based on the specific cause. You can also take preventive steps to avoid future frustrations with green pool water.


Understanding the Causes of a Green Pool


Before diving into how to treat a green swimming pool, we must first review the many things that cause a green swimming pool. These things will help you understand what to avoid in the future, and they will also help guide the type of treatment you need to fix your green swimming pool.


Algae & Green Pools

Algae growth on the inside of a pool leaking out of its skimmer. Celestial Solar logo top left.

Algae is a key culprit behind the green transformation of pool water, but did you know that algae comes in different types, each with a distinct cause and solution? Among these types, the most straightforward to tackle is green algae. Green algae is typically caused by inadequate filtration. The second variety, yellow algae, flourishes in areas with less sunlight. Yellow algae is typically found clinging to pool walls, making it more difficult to remove it. Lastly, there is black algae, which is the hardest to remove from swimming pools. Black algae is difficult to remove due to the strong roots that grow into the pool walls.


Pool Chemistry Imbalance


Balanced water chemistry is essential to maintaining a healthy pool. When pH, chlorine levels, or alkalinity are imbalanced, it creates an inviting environment for algae to flourish, leading to green water.


Chlorine levels should generally be between two and four parts per million in your pool. The recommended levels for your pool pH should be within the range of 7.2 and 7.6. Lastly, the alkalinity of your pool should be between 80 to 120 ppm.


Pollen & Metals’ Green Effect


Another lesser-known reason for your pool may be turning green is the potential presence of pollen and metal. The color of pollen is naturally greenish-yellow. When pollen accumulates and changes your pool’s color, the pool filtration system is not working effectively.


Metal is also another reason why your pool can turn green. Metal elements in your pool, such as the pump parts and ladder, can oxidize. Other times, your pool turns green because of metals when a pool is refilled with new water and “shocked” to remove algae. This color change happens if your pool water has high levels of copper or iron.


Addressing Chemical Imbalances in a Green Pool

Pool testing kit sitting along the edge of a pool. Celestial Solar logo bottom left.

We discussed earlier that many different imbalanced chemicals can cause algae, which then causes your pool water to turn green. The first step in addressing the imbalance is to use a testing kit to determine which chemical is exactly imbalanced. When balancing your pool’s pH, you can add “pH down” chemicals that you can buy from a wide array of companies. Typically, high pH levels cause algae growth, so lowering pH is vital.


In order to rebalance alkalinity levels in your pool, you can add “alkalinity increasers,” otherwise known as sodium bicarbonate. Lastly, when balancing chlorine levels, you can add unstable chlorine. Note that you should always use unstable chlorine and not stable. However, you can “shock’ your pool water to restore your pool’s chlorine levels and kill algae at the same time quickly and effectively.


Battling Algae in Murky Waters


Addressing the root causes of algae growth stops your pool water from turning green, but if algae has already taken over, more robust solutions are needed to remove it.


Shocking Your Pool: A Solution for Algal Blooms

Pool shocking tablets sitting by the edge of a pool. Celestial Solar logo bottom left.

Before beginning the shocking process, ensure maximal removal by scrubbing the algae off the pool walls first. When you break up the algae into smaller pieces, the chemicals can effectively kill algae versus when you leave the algae intact. You can also use algaecides to fight against algae if there is a smaller number of algae in your pool. Algae shield themselves with a slippery layer that makes chlorine less effective. Algaecides break this protective layer, making it easier for chlorine to eliminate the algae.


Pool shock is a chemical that contains a high level of chlorine. The amount of shock you need depends on the type of algae that is growing in your pool. One pound of shock can treat about 10,00 gallons of pool water; however, this number is meant for when your pool isn’t green. If the algae growth is light or teal green, you need 2x the normal amount. If your pool is dark green, you must use 3x the recommended amount; if your pool is black green, use 4x the normal amount. Remember that the shock strength can vary based on the company, so always check the instructions to ensure you use the right amount.


Removing Pollen & Metals to Combat Discolored Pools


In order to get rid of pollen, there are a few things you can try. First, check your pool’s filtration system and troubleshoot anything that may have gone wrong. When pollen accumulates, it can sometimes be because the filter isn’t working correctly. You can also use a water clarifier as it will gel any free-floating materials, allowing your filter to filter it out properly.


To remove metals from your pool, you can use sequestrants to ensure they get trapped in the filter. You can also use chelating agents that will remove metal particles as well.



Man with shocked and worried looks on his face holding pool cleaning equipment. Celestial Solar logo bottom right.

In conclusion, a solid grasp of the factors contributing to green pool water offers a strategic advantage in maintaining a clear and well-functioning swimming pool. By comprehending the role of various algae strains and the impact of chemical imbalances, pool owners can efficiently address and prevent the occurrence of murky water. A proactive approach involving regular water testing, appropriate chemical adjustments, and prompt corrective actions can ensure the pool remains an appealing and hygienic space throughout the swimming season. With this knowledge, you’re equipped to approach pool maintenance with a systematic and informed perspective, enhancing your pool area’s aesthetic and functional aspects. For any further information, contact us today!

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