Pool Algae

05 March 2015

Algae are microorganisms that produce organic substances from what is found in nature and in the water in your pool. Transported by wind and dust, spores of these algae are found in your pool water, even those covered. Whatever the type of algae, it multiplies rapidly in warm, sunny and in insufficiently disinfected water. Rich in dissolved minerals and often exposed to sunlight, your pool represents an aquatic paradise for these organisms. All products spoken of in this article are available in our store and our web store.

In these cases, prevention remains your best weapon. These easy but efficient steps will help you stop and prevent algae growth:

  • Always have a sufficient level of disinfectant (chlorine). Basic guideline is from 1 to 3 ppm of chlorine at all times. It is difficult to get this at all time. In this case, refer to the products you use and add them as recommended on the label. Don’t be afraid, when your water seems white, has some particles in suspension, after large uses of the pool or after warm periods to add more of the disinfectant then usual!
  • Have your pH between 7.2 and 7.6 as much as possible. Otherwise, algae will tend to form more easily (since disinfectants are largely affected by the pH). pH- or pH+? A simple test will tell you.
  • Backwash your filter at least once a week. Don’t be afraid to do it more often in special circumstances.
  • The addition of algaecide once a week will aid problematic pools to prevent algae formation. Added as recommended on the label, algaecide will help prevent and intervene against algae.
  • Scrubbing the pool walls and the bottom of the pool when you feel a sticky or slimy texture on them will help your disinfectant and algaecide to do its job and will prevent many more problems in the future since this slimy layer often precedes algae formation.

Green algae: normally stays on top of the water,it will eventually change the color of the whole pool and make it opaque. There is a large possibility that stains will form on the bottom and/or on the walls. Before the green color appears, walls will most often get a slimy and sticky feel. The origin of the formation is most likely an insufficient amount of disinfectant.


Yellow algae: also know as mustard algae, it tends to stick to walls. Being yellow, powdery and able to grow in the shade, it will more than often resist to chlorine levels. At least 5 and 15 ppm of chlorine is needed to affect these algae.


Black algae: Water might be clear but it will stick to the walls and to the bottom, on piping and in the skimmer. Most of the time, the bottom will be full of black or blue-green spots. This alga also resists to chlorine very well. One of its main characteristic is, with time, will become more difficult to remove since it will grow in a thick layer. Probable cause is the insufficient amount of disinfectant.

Pink algae: It is actually a bacteria (fungus) that lives in relatively hot water (75°F+) and needs light to grow. It will develop initially on plastic parts (PVC, skimmer basket, pump, vaccum, etc.) which make it particularly difficult to get rid of. Probable cause is the insufficient amount of disinfectant, scrubbing and bad luck to have this fungus in your environment.

Blue algae: Blue-green algae are aquatic micro-organisms that are generally present in all water pools in Quebec. It multiplies in waters rich in minerals and especially likes phosphor. When they are abundant, it forms into water blooms, even foam, on a part or the whole surface of the pool.

The treatment for these algae problems is fairly simple and mostly the same for all types of algae. Each part of the treatment is as important as the next to prevent the algae from coming back once the pool cleared up.

  • Choc treatment: A choc treatment is basically a chlorine overdose which eliminates bacteria and transforms to dust the rest. We aim for a chlorine level of about 10 ppm or more. Products such as regular chlorine, choc treatment chlorine, liquid chlorine or stabilized chlorine have on their label the amount to add for a chlorine choc treatment. If you are using anything else, make you follow the label’s instructions. Can we use algaecide to perform this treatment? Yes, but you have to put enough. The best thing to do for an optimal choc treatment is to add algaecide on top of a good amount of chlorine. This process will have to be repeated at least until you get white-ish water.
  • Scrubbing: Even if you don’t see the bottom of the pool, a blind scrubbing will help you greatly since it spreads the chemicals everywhere and exposes algae to chemical products more efficiently. Repeat this step every time you do a choc treatment.
  • Vacuuming: You will have to vacuum your pool to get rid of the residue and algae. To do so, we have to put the filter head on waste/drain mode before vacuuming. Pro tip: put your garden hose in the pool which will increase your time frame to vacuum. We suggest stopping your filtration system (pump at off) between each vacuuming sessions.  Proceed slowly to prevent dust from lifting off the ground. This step could have to be done several days in a row since it is nearly impossible to vacuum all at once (water level diminishing and dust lifting off). There is a product named Alum that can help you with the vacuuming especially when there is a lot to do. This product binds all the particles together making them heavier thus getting to the bottom more quickly and less likely to lift off the ground (follow the instructions on the label).
  • Backwash : During the treatment, it is recommended to backwash your filter each day or more if possible. This eliminates some of the particles and algae at the same time.

The process might take several days. In most cases and especially with black and pink algae, the Alum (products which binds particles together) can help you get rid of the algae problem. If the algae are still present, repeat these steps and make sure to follow them to the letter and add Alum.

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