Algae are microscopic single-cell plants that can enter the water from the atmosphere by the actions of wind and rain. There are over 30,000 different varieties of algae
The three main categories are: -
Green Algae
- usually free-floating although they sometimes colonise surfaces
The green algae are the fastest growing algae and are responsible for most 24-hour algae blooms
When pool water becomes turbid (cloudy) with algae it makes the pool dangerous to use, as it is difficult to see the bottom of the pool
As the water turns green the surfaces of the pool develop a slippery feel. The water becomes hazy, pH will shoot up and chlorine levels will drop sharply
A bloom of green algae can turn a clear, clean pool into a green swamp overnight
The pH rises as algae consume the carbon dioxide (CO2 helps to keep the pH down), and the pool surfaces will be coated with a slippery Bio-film
Once algae become visible you’re in trouble. Algae take in carbon dioxide and give off oxygen like most other plants
Most bacteria found in swimming pools take in oxygen and give off carbon dioxide
Each grows by consuming the by-products of the other, and thus the proliferation of both organisms accelerates
For this reason we use a chemical program that assures both bacterial and algae control
Mustard (Yellow) Algae
often appears on the shady side of the pool as a yellow powdery deposit. Once established, yellow algae are Chlorine resistant and can survive in the presence of 3-5 ppm of free chlorine. Superchlorination will kill mustard algae but the dead cells must be scrubbed from surfaces
Black (Blue-Green) Algae
evident by the formation of 1 to 3cm sized black (or dark blue-green) spots on the pool surfaces, especially on the grout lines or plaster. Black algae form a layered structure where the first layer (which superchlorination may kill) protects under-layers from further destruction
Black algae are similar to the algae that are found on bathroom shower tiles and in silicone seams near the bath. This form of algae is very slow growing but very hardy; it is extremely Chlorine resistant
Black algae can be controlled by the use of Copper Sulphate or a Copper Ioniser
Prevention of algae
A successful program of regular pool maintenance prevents algae from growing. This is achieved by monitoring and controlling pH and residual free chlorine in the water
Application of a general Algaecide or Algaestat is also recommended. Use Copper Sulphate at a rate of 3 grams per cubic m3. This chemical should not be applied more than 2 times per season to avoid overdosing, which can cause blue staining of the plaster or grout, green hair and blue nails
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Ken Walker - MyPoolGuru©