How to Kill Algae in a Swimming Pool

The easiest way to keep your pool clean and algae-free is to destroy the algae spores before they develop into full-on algae blooms. A good circulation system, proper sanitizer levels, weekly shocking, and routine brushing should kill most of the algae spores before they become a problem.

In the rare case that the algae does bloom, follow these quick steps to learn how to kill algae in a pool:

Test and balance your water chemistry. However, when fighting algae, Leslie’s recommends keeping your pH slightly higher than usual; somewhere between 7.8 and 8.0.

Depending on your type of filter, clean or backwash the filter to remove debris and contaminants. You will want to set the filter to run 24 hours a day while treating your pool for algae.

Brush the pool walls thoroughly, especially those areas with visible algae blooms.

Be sure to use a brush that is safe for your pools. Wire brushes are great for plaster and gunite pools, but should never be used for vinyl, fiberglass, or tiled pools. If you do not own a plaster pool, using a nylon brush will let you safely brush your pool walls.

Add a powerful shock, like Power Powder Plus or Leslie’s Chlor Brite. Follow the directions on the shock for proper dosage amounts. Large amounts of algae may require you to add up to three doses of shock over a 36-hour period. When using large amounts of shock to kill algae, water may become cloudy. This should not be a problem, and the water should clear up after running the filter.

Wait until the chlorine ppm has fallen below 5.0. After this, add a pool algaecide like Leslie’s Algae Control and brush the pool again.

After brushing, vacuum the pool. If large amounts of algae are suspended or floating on the surface, it may be a good idea to add a flocculent like Ultra Bright. This will cause the particles to bind together and fall to the bottom so they can be vacuumed easily.

Continue to run the filter until algae is cleared from your pool. If algae persists, continue to shock and brush vigorously until the algae is gone. You can also bring a water sample into your nearest Leslie’s store for a water test and advice on clearing up your pool.

Recommended Products

Bucket of Leslie's 3


Leslie's Power Powder Plus 73 Chlorine Shock


Leslie's Perfect Weekly


Facebook  Twitter X  YouTube  Instagram
Leslie’s makes every effort to provide accurate recommendations based upon current ANSI/APSP/ICC-5 2011 (R2022) standards, but codes and regulations change, and Leslie’s assumes no liability for any omissions or errors in this article or the outcome of any project. You must always exercise reasonable caution, carefully read the label on all products, follow all product directions, follow any current codes and regulations that may apply, and consult with a licensed professional if in doubt about any procedures. Leslie’s assumes no legal responsibility for your reliance or interpretation of the data contained herein, and makes no representations or warranties of any kind concerning the quality, safety, or suitability of the information, whether express or implied, including, without limitation, any implied warranties of merchantability or fitness for a particular purpose.