Types of Swimming Pool Algae and How to Treat Them

Swimming pool algae is an unsightly problem that plagues many residential swimming pools. However, when properly treated, swimming pool algae can be easily treated and banished from a pool. In my many years working in the retail swimming pool and spa industry, I have seen numerous cases of algae develop. It is important to identify what type of algae has infected your pool before proceeding with a plan of action.

There are 3 main types of swimming pool algae. The first and most common type is green algae. Green algae is a free floating algae. While it may hover slightly around the sides of a pool or the steps, it is not actually attached to anything. Green algae is most common because it is very opportunistic, meaning any faltering in your pool’s chemistry or care will usually spark green algae’s presence. This algae is also frequently spotted after a rainstorm with lightning. Lightning will not only reduce the free chlorine in your pool, but lightning gives off nitrogen, which algae feed on.

The second most common type of algae is yellow or mustard algae. This algae is similar to green algae but lacks chlorophyll, the chemical that produces the green pigment in plants. This algae is less common because it takes a longer time to develop. However, once mustard algae takes a hold, it can be difficult to treat, sometimes requiring multiple treatments to fully eliminate.

The third and most dreaded kind of algae is black algae. Black algae affixes itself to the sides and the bottoms of a pool. It may have a black or very dark blue/green appearance. To rid yourself of this type of algae, it is best to use an algaecide specifically made for black algae. However, the addition of algaecide alone is usually not enough to cure this nuisance. Black algae develops a waxy coating over itself making it harder for algaecides to penetrate. A good brushing of all areas affected by this algae with a pool brush (daily, if possible) will help eradicate your black algae problem and allow the algaecide to do its job.

There are a few tips to remember when treating any algae problem. First, the best time of day to kill algae is during the warmest and sunniest part of the day when algae is growing and active. Secondly, algae c an sometimes be blamed on poor filtration. Make sure that your filter is at peak performance. If it is a sand or D.E. filter, make sure you have fresh filtering media or sand. Exceptionally dirty filters can cause poor circulation, which is the perfect environment for algae of any type.

Thirdly, exercise a little patience. Most algae problems did not occur overnight. Therefore, it may take sometime to fix as well. Once you do rid your swimming pool of algae altogether, be sure to keep adding a “maintenance” dose of algaecide to your pool according to the directions on the chemical bottle. This will ensure that you will continue to have an algae-free swimming season.