Algae is a major concern for pool owners. Algae is a one-celled plant that can grow in your pool if conditions are favorable. The most common myth concerning algae growth in pools is that it is ONLY a result of low chlorine (or its alternative). Although this is definitely a major cause of algae, it is not the single contributing factor.
Despite water treatment facilities, actual traces of algae may very well be present in the tap water that is used to fill your pool. Therefore, it is always a good idea to add an algaecide and to shock your pool after it has been filled or refilled. Yet another contributing factor toward algae growth are millions of microscopic algae spores that are carried by wind, eventually falling into your pool, where they will grow into outbreaks of algae if conditions are favorable.
A few of these favorable conditions are environmental. Algae, like all plants, need light and food in order to survive and grow. Temperature, humidity, sunlight, and nutrients (food) foster algae growth. Temperature, humidity and sunlight are self-explanatory. Nutrients consist of lawn fertilizers and other industrial products that are carried by wind and blown into the pool. Nutrients also consist of certain minerals that are already present in water. Since water chemistry relies on some of these certain minerals to be present, they cannot simply be removed from the water.
Here is a possible sequence of events: Algae spores will blow into your pool, where they are supported by temperature, humidity and sunlight. The algae spores then consume various nutrients. From temperature, humidity and sunlight, as well as from nutrients, the once unnoticeable algae spores have now grown into actual algae.
In addition to these environmental factors, other factors, such as limited water circulation, poor filtration, a neglect of routine pool maintenance, heavy bather loads, a neglect of overall water chemistry, neglect of shocking, and of course, insufficient levels of chlorine (or its alternative), also make conditions favorable for algae growth.
Algae is not harmful to swimmers. It just causes the appearance and integrity of your pool to suffer and occupies time to correct. If you do get algae, you are not alone; it has been seen in pools of some of the foremost authorities on pool care and maintenance. Rest assured, any algae can be killed, but not without a few days of continued effort and time. Therefore, it is best to begin with a discussion on the necessary steps to prevent algae growth. An ounce of prevention is worth a hundred pounds of cure.