Last Updated on April 19, 2017

how to clean green pool

Nothing puts a damper on summertime pool fun like lifting your pool cover only to see you have the dreaded green water.  Green pool water happens because algae have taken over when chlorine levels dip below optimal levels.  Don’t despair. There are easy effective fixes to get your pool sparkling and blue again.


  1. Clean your pool.  For your treatment to be effective, break up the algae your pool brush, completely brushing the floor and sides of the pool. This will also speed up how quickly the chemicals work.
  2. Filter. Clean and check filter and run it before and during the entire treatment process. Remove any dirt and debris from the filter and skim visible debris from the surface of the pool water. A well running filter is critical for the treatment process. Backwash the filter if necessary.
  3.  Test the water. Check the levels.  Optimal chlorine levels are between 1.0 and 3.0ppm.   As a pool owner you know it is always a battle between chlorine and algae. When your pool is green the algae has won. Algae develop when the chlorine level drops below 1ppm.
  4. Treat.  Use algaecide or chlorine shock.  You can choose to do one or both.


Let’s look at what algaecide does.  This is a fast and easy way to treat, and prevent, algae overgrowth and ultimately has the benefit of being able to enjoy your pool with less chlorine.  The ammonia version is less expensive than the metallic version and also is less likely to stain your pool.  The ammonia formula tends to be a little sudsy so be prepared for that if you select it.  Make sure whichever formula you choose that it has at least 30% of the active ingredient or it won’t be effective in removing the green stuff.   If you happen to have black algae you will need a different formulation.  Once you treat using algaecide and still would like to do a chlorine shock treatment, wait a full 24 hours to give time to work.


A shock treatment is effective without pre-treating with algaecide. Chlorine shock should be doubled for green water treatment. If your water is very dark green you should triple the dose.  Follow instructions on container for amount recommended for your pool size. Premix the chemical granules in a bucket so they dissolve first or they will sink to the pool bottom and not treat the algae problem effectively.  Once you add the dissolved granules to the pool, help with skimmer or filtration to get it dispersed into the water quickly.


  1. Remove. Algae are dead when it loses its green color and either sinks to the bottom or floats to the top.  Vacuum them out of the pool and clean out the filter thoroughly so they cannot take hold again.


Steps to prevent future green water episodes:


Make sure your filters are optimally clean. Check skimmer and pump filter baskets frequently for debris.

Keep chlorine levels between 2-3.0ppm.  If you tend to be forgetful about checking try using a floating chlorinator.   Set an alarm on your phone to check levels once a week so you don’t have to shut your pool down to treat algae.


Brush regularly. Do this when you check your chlorine levels weekly to make sure no algae is taking hold to the bottom or sides.  If you have children old enough, let them help out with this step to keep their summertime fun in good working order.  Make sure the brush you have is designed for your type of pool so you don’t damage the structure.


Remove the food that algae eat: Phosphates.  You can’t avoid them getting into your pool. Organic matter/debris, lotions and oils on the skin of swimmers and tap water are some of the ways phosphates get into your pool and feed algae.  Healthy chlorine levels should keep phosphates in check but if they get out of hand there are treatments commercially available to remove them.