Management and treatment of swimming pool algae, mustard algae, black algae, algaecides and green algae
Algae is a common problem in swimming pools. What is; what the different types are and how it is successfully prevented and treated. First of all, algae are a form of unicellular plant. Some are aquatic (live in water), others are not. Algae use the process of photosynthesis to make their own food. Algae come in a wide variety of colors and shapes, making them adaptable to almost any condition. Although some forms are virulent, especially black or mustard algae, most are harmless and present little more than a nuisance to most pool owners. Due to the microscopic size of algae, it takes literally millions of these plants to accumulate in plain sight! At that point it may be too late and too expensive to correct. Prevention of algal blooms is the best solution.
green algae: The most common form of algae we treat in swimming pools is “green” algae. Green algae (varying in color from blue-green to yellow-green to dark green) can float freely in the water (turning the water a fuzzy green) or can adhere to walls (spots of green). Wall-clinging varieties range in severity from small patches on pool walls and bottoms to virtually covering the entire pool surface. Green algae have the ability to clog filters and can even cause surface damage if left untreated. Green algae can be treated quite easily and quickly with a proper and aggressive anti-algae treatment.
A relative of the regular green algae is the “small cell green algae” (SCGA). The difference is seen in these areas: 1. The water remains relatively clear. Many treat the problem (without proper analysis) as a copper or ore problem; however, metal chelators will not show any effect. 2. When treating with chlorine, the chlorine seems to “disappear”. SCGA is very resistant even to high levels of chlorine.
Other types of mid-summer green algae to notice are “green spots” around the pool, especially in shaded areas. The water is almost always “very clear”. The water may have a “stinging” sensation. These are normal green algae, usually caused by the owner’s inattention; i.e. not following a weekly maintenance routine like the 3 step once a week program combined with very low pH and very low total alkalinity.
Treatment: Have the water properly tested. BALANCES THE WATER IN THE POOL. Pools treated with chlorine or bromine should apply an aggressive chlorine treatment (BioGuard Burn Out® or Smart Shock®) and use a good quality algaecide such as Back Up®, Algae All 60® or Banish® in extreme cases. Pools treated with SoftSwim or other Biguanides should top up their Bactericide “B” level, add a double dose of algaecide “A”, and add a double dose of shock or “C”. Follow either method with Optimizer Plus® (a borate product similar to ProTeam Supreme). Treatment of algae with sodium bromide should be discouraged (sodium bromide treatments can, over time, cause a chlorine demand problem).
“Black Algae” (actually blue-green algae) forms in the cracks and crevices of pool surfaces, especially plaster finishes. We typically find black algae growing in, but not limited to, shaded areas of the pool. Black algae is most typically found in pools with a concrete or plaster finish; it is very rare to find it in pools with vinyl liner. It is known for a heavy slime coating and “skeletal growths” that make it impervious to normal chlorine levels. When viewed in a pool, the water remains relatively clear, however almost all customers notice a high chlorine demand (using much more chlorine than normal). When brushed, the “black algae” will be difficult to move and even if it appears to have been removed, the black algae will most likely return to the exact same places within 24 hours.
What we are beginning to understand is that Black Algae is “aided” by swimming pool biofilms. As biofilms build up on pool surfaces, they act as a kind of “grow bed” that provides nutrients and a “soft” place to take root. Biofilm removal helps dramatically in the long-term treatment of black algae. The more biofilm is continually removed and removed, the less likely Black Algae can establish itself.
Treatment: Have the water properly tested. BALANCES THE WATER IN THE POOL. Before and during treatment, the algae MUST be brushed thoroughly to “break up” the layer of slime that covers and protects the Black Algae cell. During treatment, chlorine level MUST be kept above 3.0 ppm (this may require daily pool flushing) AND affected areas MUST be thoroughly brushed 2-3 times daily to allow chlorine treatment to penetrate the seaweed. TRUE Black Algae is highly resistant to treatment and can be transferred from one pool to another via swimsuits and pool toys. If these critical steps are not followed, the treatment will not work. Pools treated with chlorine or bromine should apply an aggressive chlorine treatment (Burn Out® or Smart Shock®) and use a good quality algaecide such as Back Up®, Algae All 60® or Banish® in extreme cases. Pools treated with SoftSwim or other Biguanides should top up their Bactericide “B” level, add a double dose of algaecide “A”, and add a double dose of shock or “C”. Keep track of any of the methods with Optimizer Plus®. Treatment of algae with sodium bromide as mentioned above should be discouraged.
“mustard seaweed” it is probably the MOST misdiagnosed form of algae. Mustard algae is a chlorine-resistant form of green algae (yellow-green to brown in color) typically found in sunbelt areas. It often looks like dirt or sand at the bottom or sides of a pool. In our market area (Fairfield County CT), the number of TRUE mustard algae cases we treat can be counted on ONE HAND most seasons. Mustard algae are prevalent in sunbelt areas. Mustard Algae has certain characteristics: it can be removed with a brush very easily, but it quickly returns to the same place.
Be aware that “algae” may be returning to the same spot due to a dead spot in the pool. Make sure you have good circulation throughout the pool.
Although it typically creates a high chlorine demand, it has been known to survive in high chlorine levels, greater than 3.0 ppm. It is extremely important to remove mustard algae growth from equipment (including the backs of underwater lights and ladders) and swimwear to prevent crossover or recontamination of other pools. Pool equipment can be left in the pool during product application or cleaned separately with a mild cleaning solution. Rinse thoroughly if equipment is used in a SoftSwim® pool. Bathing suits must be washed with detergent as indicated on the garment label.
Treatment: Have the water properly tested. BALANCES THE WATER IN THE POOL. Before and during treatment, the algae MUST be brushed thoroughly to “break up” the slime layer, as with Black Algae. If this critical step is not done, the treatment will not work. Pools treated with chlorine or bromine should apply aggressive chlorine shocks such as BioGuard Burn Out® or Smart Shock® and use a good quality algaecide such as Back Up®, Algae All 60® or Banish® in extreme cases. Pools treated with SoftSwim or other Biguanides should top up their Bactericide “B” level, add a double dose of algaecide “A”, and add a double dose of shock or “C”. Keep track of any of the methods with Optimizer Plus®. Treatment of algae with sodium bromide as mentioned above should be discouraged. Click here to view all algae treatment products.
The best way to prevent and control algae is to maintain good pool care. Good pool care means following the 5 Keys to Pool Care (look for our published articles on these topics): 1. Have and maintain good water circulation in all parts of the pool. 2. Filter the pool a minimum of 8 to 12 hours daily. 3. Clean the pool regularly by vacuuming and brushing all surfaces. 4. Test the water at least 2 times a week. The tests tell you what is happening with the water. Make adjustments immediately when necessary. 5. Maintain good water chemistry. Chlorine or other disinfectant in its correct ranges, pH 7.4 – 7.6, Total Alkalinity 100 – 150 ppm, Calcium Hardness 200 – 300 ppm. Weekly (every week throughout the season): Shock the pool with the appropriate shock treatment and add a maintenance dose of a good quality algaecide (do not use the algaecide from the gallon jug, they are mainly colored water).