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Algae are microscopic plant life. There are many types of algae, yellow, green, brown, or
black; thousands of species of algae exist. Green algae are the most common type and the
easiest to get rid of.
Green algae can appear in patches or create an all-over cloudy green
shade of water.
Pink slimy algae are actually not algae but fungus bacteria, often appearing
as streaks or spots in corners and crevices. Sometimes it appears as a pink or orange colored
ring around the skimmer or waterline.
See Pink Slime or Water Mold for details and treatment.
Mustard algae prefer shady areas like pool step corners, along the walls and under the pool
lights, ladders or other fixtures. Black algae often appear as dark colored spots on the walls or
floor. Temperature, sunlight, pH, sanitizer level and the presence of carbon dioxide,
phosphates and nitrates all affect the presence and growth rate of algae. Algae can be
introduced into the pool by rain or wind, leaves and organic material, even fill water.
In early
stages of algae infestation you may notice the water circulation slowing as the filter is removing
algae spores, the filter pressure builds and the return flow decreases.
In all cases it is much easier and better to prevent the growth of algae than to cure it.
To prevent algae from growing in the first place requires regular pool maintenance, proper
circulation and filtration; keeping the pH and free chlorine residual or other sanitizer at the
proper level, keeping the pool clean and vacuumed, weekly shocking and adding a
maintenance algaecide, algistat or specialty chemical to help prevent algae growth.
proper sanitizer levels will prevent most algae growth
there are some strains that are
resistant to chlorine and other sanitizers.
That is why it is a good idea to regularly add a
dosage of a maintenance algaecide or a specialty chemical. Although you are not able to test
for algaecide levels in the water, regular use will be an effective deterrent to algae growth.
Maintenance algaecides may cause foam on the surface of the water due to their ability to
decrease surface tension.
The foam is normal and short lived and will gradually disappear
with filtration.
Maintenance algaecides often have a lower percentage of active ingredient and
work best in preventing algae, as an algistat rather than as a treatment for active algae
There are a variety of specialty chemicals available today, such as phosphate
removers, that can also be used to prevent algae growth.
For more information go to
Specialty Chemicals
If you develop an algae problem a professional water analysis is recommended to help
determine the course of treatment AND the cause of the algae.
Your pool professional will
help you determine the type of algaecide needed based on the algae present and your pool
As mentioned above, you can treat an existing algae problem with algaecides or
specialty chemicals.
General instructions for treatment using algaecide are listed on the
following pages.
BIGUANIDE users CANNOT use certain types of algaecide (copper or silver
based) and should only use the algaecide recommended with their brand specific program.
Algaecides kill algae working hand in hand with your sanitizer to help control and prevent algae
growth. There are many different types of algaecides available; some are made to specifically
fight certain types of algae. The key to choosing the right algaecide is to follow the
manufacturer’s directions and to maintain a regular amount of algaecide in the water during
Polymer based algaecides from 30-60% are non-foaming and effective in both
prevention and killing of many types of algae.
Copper, silver and magnesium based
algaecides are often recommended for killing stubborn algae such as black or mustard.
Caution should be taken when using mineral based algaecides such as copper or silver in