It’s every pool owner’s nightmare—one day your water is clear and sparkling, and the next it looks like a swamp or a murky mess. Whether your pool has turned green from algae or just looks cloudy and uninviting, a good shock treatment is often the fastest way to bring it back to life.
Shocking your pool means adding a high dose of chlorine or another chemical oxidizer to kill off bacteria, algae, and other contaminants. But not all pool shocks are created equal. Some are best for minor cloudiness, while others are strong enough to take on a full-blown green pool. In this guide, we’ll break down the best pool shock treatments for green and cloudy water, how they work, when to use them, and what to avoid—so you can get back to enjoying your pool ASAP.
Cal-Hypo Shock: Best for Killing Algae Fast
Calcium Hypochlorite, or cal-hypo, is one of the strongest and most commonly used shock treatments, especially for green pools. It contains around 65–75% available chlorine and works quickly to kill algae and bacteria.
This type of shock is ideal for pools that have turned green or are starting to grow visible algae. It’s affordable and easy to find, but it does increase your pool’s calcium hardness, so it’s best not to use it too often if you have hard water or a vinyl liner.
When to Use:
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Pool has turned green or dark green
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You see algae on the walls or floor
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After heavy rain or a pool party
Dichlor Shock: Best for Stabilized Chlorine
Dichlor, or sodium dichloro-s-triazinetrione, is a type of shock that contains cyanuric acid (stabilizer), which protects chlorine from being destroyed by the sun. It’s slightly gentler than cal-hypo and dissolves quickly, making it ideal for routine shocking or slightly cloudy water.
If your pool is a little hazy but not green, dichlor can be a more balanced option that won’t raise calcium levels or damage liners.
When to Use:
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Slightly cloudy water
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Regular weekly or biweekly shocking
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Pools with low CYA levels
Non-Chlorine Shock (Potassium Monopersulfate): Best for Cloudy Water
If your water looks dull or cloudy but there’s no sign of algae, a non-chlorine shock is a great choice. Made from potassium monopersulfate, this oxidizer eliminates chloramines and organic waste without raising chlorine levels. It’s safe to swim shortly after treatment and great for regular maintenance or quick cleanup after a heavy bather load.
When to Use:
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Cloudy water without algae
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Want to swim sooner after shocking
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Pool smells like chlorine (from chloramines)
Liquid Chlorine: Best for Large or Commercial Pools
Liquid chlorine is essentially the same thing as bleach, but in a higher concentration. It’s a powerful and fast-acting shock treatment often used by professionals. It doesn’t leave behind residue, and it won’t affect calcium levels—but it does degrade quickly in sunlight and doesn’t contain stabilizer.
This makes it ideal for large or heavily used pools that need rapid sanitation.
When to Use:
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Commercial or public pools
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Very large home pools
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Want fast results with no residue
Multi-Purpose Shock Products: Best All-in-One Solution
Some shock products combine chlorine with clarifiers, algaecides, or flocculants to solve multiple issues at once. These are great for pool owners who want a quick fix without juggling multiple chemicals.
While they’re not as strong as pure cal-hypo or dichlor, they offer convenience and can clear up minor cloudiness or algae blooms with less effort.
When to Use:
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You’re not sure what’s wrong
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Want a convenient solution
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Minor green or cloudy water
Tips for Effective Shock Treatment
No matter which shock you choose, here are some tips to make it work better:
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Test first: Know your chlorine, pH, and stabilizer levels before you shock.
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Brush your pool: This loosens algae and helps the shock penetrate.
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Run your filter 24/7: Especially after shocking, to circulate and clean.
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Shock at dusk or night: UV rays can break down chlorine quickly.
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Wait to swim: Always follow the product label to know when it’s safe to re-enter the pool.
Conclusion
Dealing with green or cloudy pool water doesn’t have to be overwhelming. With the right pool shock, you can transform murky water into a crystal-clear oasis in just a day or two. Whether you go with a powerhouse like cal-hypo, a balanced option like dichlor, or a gentle non-chlorine oxidizer, the key is choosing the treatment that matches your specific problem. So grab your test kit, brush down those walls, and get ready to enjoy your pool again—clean, clear, and hassle-free.