Every pool owner has, at one time or another, done
battle with the occasional algae bloom. Algae spores constantly enter
the pool, brought in by wind, rain or even contaminated swimsuits or
equipment. When conditions are right, an algae bloom can occur seemingly
overnight. These conditions include out of balance water, warm temperatures,
sunlight and presence of nitrates and/or carbon dioxide. Of course,
a lack of proper circulation, filtration and sanitation may be the primary
cause of the algae. The best process is one of elimination.
Algae is a living aquatic creature that multiplies
rapidly on warm, sunny days. Containing chlorophyll, algae utilize photosynthesis
to grow. That is, they take in carbon dioxide and expend oxygen as a
Caused By Algae
The first noticeable problem is that no one seems
to want to go swimming. The second problem is that it requires work
and effort and money to rid the water completely of algae. It is therefore
best to use preventative chemicals and techniques, described later.
Algae can cloud and color the water, making rescue attempts difficult
and reducing depth perception of a diver. Algae itself is not harmful
to swimmers, but pools with algae may also be harbor to pathogens like
In addition to clogging up sanitation pathways in
the water, algae also clogs up the pores in a filter, decreasing filter
effectiveness and requiring more backwashing or medium replacement.
Algae creates a chlorine demand in the water for itself, actually consuming
chlorine that should be working on other contaminants. Algae are kind
of like weeds in your garden. Unsightly, unwanted space takers that
create more work for the gardener, and sap up nutrients and resources
from the flora we wish to grow.
Types of Algae
There are over 21,000 known varieties of algae!
In the pool business we avoid all of the complication by referring to
algae by the color they exhibit.
GREEN ALGAE: An extremely common variety, green
algae will usually rear its ugly head immediately following a hazy condition
in the water from a lack of proper filtration and/or sanitation. It
is frequently found free floating in the water, although it also will
cling to the walls. It reduces water clarity and is thereby distinguished
from severe copper precipitation, which will impart a clear, green color
to the water. Varieties of green algae also appear as "spots"
on surfaces, particularly rough areas, or places where circulation is
low. They also show up as "sheets", where large wall sections,
or even the entire pool, is coated in green slime...UGH!
YELLOW ALGAE: A wall clinging variety, also called
mustard algae, is usually found on the shady side of the pool. It is
sheet forming, and can be difficult to eradicate completely. Once begun,
a pool owner could spend the entire season fighting yellow algae; reinfection
is common. This variety is resistant to normal chlorine levels and must
be dealt with firmly. Hit it hard!
BLACK ALGAE: Perhaps the most aggravating strain
of algae, it has been compared to herpes; "once you've got it,
it's there for life". This is not entirely accurate, but the difficulty
in eradication is due to the strong roots and protective layers over
top of the black algae plant. Black algae will appear as dark black
or blue/green spots, usually the size of a pencil eraser tip. Their
roots extend into the plaster or tile grout, and unless the roots are
destroyed completely, a new head will grow back in the same place. The
heads also contain protective layers to keep cell destroying chemicals
from entering the organism. Like yellow algae, black strains can bloom
even in the presence of normal sanitizing levels and proper filtration.
PINK ALGAE: Not really an algae at all, but a form
of bacteria. Appears as spots or streaks in corners and crevices. It
is slow to spread and rare that it will bloom over an entire pool.
Proper chemical balance and sanitizer residuals
will prevent many opportunities for algae to bloom. high pH and low
chlorine (or other sanitizer) can give algae a great start to genesis.
General cleanliness of the pool is also important. Organic material
and bacteria can contribute to algae growth. Regular brushing of seemingly
clean pools is not only good exercise for you, but prevents dirt from
harboring in the pores of the plaster, which is a good start for an
The use of specialty chemicals or algaecides is
recommended to provide a back up to normal sanitation and filtration
processes and is completely necessary for many pools. These chemicals
are described below:
POTASSIUM TETRABORATE: This chemical, when added
to the pool water in proper dosage, prevents algae from converting carbon
dioxide into the fuel it needs for growth. Manufactured under the trade
name Proteam Supreme. An extraordinary product.
CHITIN: Not an algaecide (meaning to kill algae)
per se, but its properties might be called algaestatic (that is, to
prevent algae growth). Chitin has the ability to coagulate and remove
a wide variety of suspended materials and impurities form the water.
This allows the sanitizer to more effectively kill contaminants unobstructed.
It also improves the effectiveness of the filtration equipment. Sold
under the trade name Sea-Klear, chitin can be a valuable weapon in your
1. QUATERNARY AMMONIUM COMPOUNDS: A low grade type
of algaecide, Quats, as they are called, will usually have "10"
somewhere on the bottle, representing 10% active ingredient. Although
available at a lower cost, quats tend to produce a small amount of surface
foaming. They are most effective as an algaestat, that is, as a prevention,
not a cure.
2. POLYMERS: Polymers are long, complicated chemical
chains that behave in water both as an algaestat and an algaecide. They
are available in percentage strength of 30-60%, are non foaming, and
work well as general, all around algae treatments. Poly-Quats are a
blended compound of polymer and quats.
3. COPPER BASED: Copper is a proven algaecide and
algaestat. Available in varying non foaming strength of 3-10%. It works
very well on all types of algae, but it has the drawback of staining
white plaster surfaces a light blue/green color if it precipitates out
of solution. Most copper based algaecides are chelated, which means
that agents have been added to prevent this, such as Lo-Chlor Algaecide.
4. SILVER BASED: Silver has been shown to be an
effective bacteriostat, which means that it works to prevent bacteria
from reproducing. Non foaming and effective with pink algae. In high
doses, reactions with sunlight can cause colloidal silver to deposit
as black stains on white plaster. When using copper or silver algaecides,
the use of a sequestering agent is recommended.
These are not algaecides, but work to provide a
synergistic boost to hypochlorites when added separately, but at the
same time. Sold under trade names like Mustard Buster, Yellow-Out or
Yellow Treat, it is most effective on, you guessed it, yellow algae.
Since it is not an algaecide, the makers are not required to tell what
it is made of, but we do know that it works quite well, in conjunction
with a little brushing and vacuuming on your part.
First off, balance your water, paying particular
attention to pH. Secondly, check your filter system and clean if necessary.
Adjust valving for optimum circulation and allow it to run 24 hours
a day until the pool clears. Turn on automatic cleaners to help stir
things up. Backwash as necessary.
For suspended green algae, shock the pool...hard.
Put in as much hypochlorite as it takes to turn the pool a cloudy, bluish/gray
color . Brush the walls and floors towards the main drain. Backwash
the filter when the pressure gauge indicates the need. Using a flocculent
may be a good choice if the pool is extremely "swampy". If
you cannot see the bottom of the pool, and it is filled with leaves
and debris, it may be wise to drain the pool, acid wash and refill it.
(Please Note that chlorine is a
bleaching agent and therefore could cause fading or spotting on vinyl
liners. It is therefore suggested that you check with your liner's manufacture
prior to super-chlorinating your pool).
After the chlorine level has come down below 5 ppm,
add an algaecide and brush the pool again. When it all settles, vacuum
the pool (to waste, if possible). Check and rebalance the pool water
For algae which is not suspended, but only clinging
to the walls, follow the same advice above, first shock with brushing,
then add an algaecide, brush again, vacuum to waste (preferred) or vacuum
and then backwash the filter. Use of a steel bristled brush is recommended
for algae on plaster pools (use nylon brushes on vinyl). Filter, Filter,
For black algae, the brushing part is very important.
You must tear through the protective layers so the chemicals can destroy
the plant from the inside out. Pumice stones work well to knock off
the heads of black algae. (Don't forget to vacuum them up later, and
backwash them out of the filter ASAP). Also effective on the black algae
nodules is sprinkling granular trichlor over the spots (of course if
they're on the wall this is next to impossible). Rubbing the spots on
the walls with a trichlor tablet or stick can also be effective to knock
off the heads and get trichlor directly to the roots. Follow up with
a dose of copper algaecide, or high strength polymers. Simazine, an
herbicide, was a very effective black algae treatment, but is no longer
available in America.
If algae has been an ongoing problem in your pool
for several years, you may do well to drain the pool. Many years of
algae builds up dead algae cells and lots of other solids in the water
that contribute to its rejuvenation. Acid washing and/or pressure washing
is preferable once drained, to kill the roots of the algae embedded
in the plaster. NEXT: change the sand if you have a sand filter or change
the cartridge if it is a cartridge type. Sand should be changed every
5-7 yrs (or every 2 if you use baquacil), and cartridge filters should
have new elements every 1-2 years. If you have a DE filter, you should
remove the elements, spray clean, soak in a 10:1 water/bleach solution,
rinse and replace. A well functioning filter will prevent algae.
Another item to look at is the method of sanitation
and the type of filtering you have. Far too many pools out there were
sold with marginal filter systems, meant to run 24 hrs per day. Well,
these systems get old and tired, or the new owners only run it 12 hrs
per day (or less). For good algae prevention, we need a combination
of good filtration, sanitation and circulation. It may be time to consider
changing the old pump and filter. It's cheaper and easier to pay a little
up front for more chemicals, electricity or better equipment than all
the money and aggravation spent on fighting algae blooms.
| Problems Caused by Algae | Types
of Algae | Algae Prevention
|Algaecides | Chlorine
Enhancers | Killing Algae
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