Types of Pool Algae: Identification & Treatment for Commercial Pools

Algae are a threat to any commercial pool, requiring proactive control measures to ensure guest safety, water quality, and regulatory compliance. Any facility manager or commercial property owner must understand the nature of algae and the control measures necessary to prevent growth.

What Is Algae, and Why Does It Grow in Pools?

Algae are simple aquatic organisms that are typically single-celled, but the group also includes multicellular varieties such as seaweed and kelp.

Three key factors accelerate algae growth:

• Warm water: Algae love higher temperatures, which is why growth can be a concern in commercial swimming pools.
• Stagnant water: Commercial pool filtration systems can help combat algae growth when they work efficiently.
• Chemical imbalance in water: This would include incorrect sanitizer levels, high pH, and nutrients that serve as a food source.

Controlling growth in a commercial pool is critical because it directly impacts:

• Guest safety: An algae bloom creates slick surfaces, increasing the risk of slips and falls.
• Water clarity: Algae feeds on chlorine, promoting the growth of potential pathogens in the pool. This can lead to cloudy and unhealthy water.

It is a disastrous combination for commercial pools, leading to guest dissatisfaction and failed regulatory inspections. The key to controlling algae growth is proactive water management. The combination of consistent water testing, efficient pool filtration, and the routine application of preventive treatments is the cornerstone of maintaining a healthy, profitable business.

Common Types of Pool Algae

Finding the right algae treatment methods depends on correctly identifying the type of bloom affecting the pool water.

Green Algae (Most Common)

Green algae are free-floating algae that can quickly turn the water cloudy or a murky green. There may be slimy green patches of growth on the pool walls and floor, as well.

Green algae are usually caused by:

• Low sanitizer levels: Insufficient free chlorine or other sanitizers allow the algae to reproduce rapidly. The growth can take hold within hours if chlorine levels drop.
• Poor water circulation: Pools with stagnant, dead spots due to insufficient filtration are prone to green algae growth. The poor circulation prevents the sanitizer from reaching all areas of the pool.
• Warm water and direct sunlight: Warm temperatures can speed up algae growth.

Best treatment practices include:

• Shock treatment: This involves administering a heavy dose of chlorine to raise sanitizer levels and chemically treat living algae.
• Brushing and vacuuming: Scrub the pool surface to lift algae and then vacuum the debris.
• Improve circulation and filtration: After treating the water, run the pump continuously for 24 to 48 hours to filter out the dead algae and treat the entire volume of water.

Once the pool is rid of the green algae, consistent water management can keep it at bay.

Mustard / Yellow Algae (Chlorine-Resistant)

Mustard or yellow algae are more difficult to treat than green algae. It is easily identified by its dusty yellow or brown blooms, which cling to pool walls and floors.

What makes mustard algae tricky is its resistance to chlorine. Even pools with the recommended levels of sanitizer can experience yellow algae growth. The algae spreads easily to cleaning equipment, floats, and even swimsuits, leading to frustrating recurrences.

Treatment for yellow algae requires an aggressive and layered approach:

• Strong shock treatment and algaecide: Shocking the pool at high levels, often 15 ppm or higher, may be necessary to control the growth. Combine the traditional shock treatment with a specialized algaecide for the best results.
• Thorough brushing of all surfaces: Rigorously brush all the pool surfaces immediately after the shock treatment. This will expose the algae to the chemicals.
• Disinfect everything that goes into the pool: Clean swimsuits, toys, floats, and cleaning tools prevent the transfer of algae spores back into the water.

Prevention of mustard algae growth:

To prevent this algae growth, pool professionals should maintain higher chlorine levels in warm climates. Also, periodically shock the pool even if the water appears clear.

Black Algae (Most Difficult to Eradicate)

Black algae are the most difficult to treat in a commercial pool environment. It can require time and commitment to remove safely.

Two characteristics make black algae different from the other varieties:

• Protective outer layer: It has a thick, slimy cap layer that shields it from chemical treatments. It can also protect bacteria, which makes the algae more of a safety and health hazard.
• Deep root system: Black algae form deep roots that push through the pores of pool surfaces, such as concrete, tile grout, and plaster, causing structural damage and allowing the algae to regrow even after a seemingly successful treatment.

Treatment for black algae must be aggressive to eliminate this threat:

• Scrubbing: Scrub the pool with a wire brush or other specialized tool. It must be able to break through that protective cap to allow for effective chemical treatment.
• High-level chemical dosing: High-level doses of chlorine and black algae-specific algaecides are essential.
• Continuous filtration during the treatment: This ensures the chemicals reach all areas of the pool and filter out dead organisms.

Preventing black algae growth requires maintaining a healthy, balanced pool environment. Surfaces must be clean, and the water must be well circulated. The water must maintain proper calcium hardness and pH levels to prevent pool surfaces from deteriorating and to prevent algae from taking root.

How to Prevent Pool Algae Growth in Commercial Pools

Algae prevention is the most cost-effective strategy for any commercial pool. Following a strict checklist for pool maintenance:

• Consistent water chemistry: Test the water to maintain proper balance and adjust when necessary. Parameters should include:
• • Chlorine: Maintain a stable free chlorine level between 1–3 ppm.
  • pH: Keep pH between 7.2 and 7.6 for optimal chlorine effectiveness.
  • Alkalinity: Maintain total alkalinity between 80 and 120 ppm to prevent swings.
• Filtration: Run filtration systems at least 8–10 hours per day.
• Weekly cleaning: Focus on brushing walls, steps, and corners.
• Shocking: Shock the pool weekly during high use or hot weather.

Conduct daily water testing for commercial pools. Residential pools should do a weekly test.

When to Call a Professional Water Treatment Specialist

When the algae problem goes beyond what standard equipment and commercial pool chemicals can  handle, it is time to call in a professional water treatment specialist like Aqua Management Partners. Some algae problems will require specialized services to prevent structural damage and to maintain compliance, including:

• Recurring algae outbreaks
• Visible algae growth, especially black algae
• Persistent water instability

Rely on the experts at Aqua Management Partners to provide your commercial pools with:

• Professional water analysis to determine the root cause of the algae growth
• Commercial-grade algaecides and treatment plans that can eradicate even chlorine-resistant strains from swimming pool surfaces

Aqua Management Partners also provides long-term maintenance partnerships that focus on  getting rid of algae, preventing future regrowth, ensuring efficient filtration, and maintaining a chemical balance that meets the local regulatory standards.