What is Black Algae and How to Prevent It?
What is Black Algae and How to Prevent It?
Discovering dark, stubborn spots on your pool’s surfaces can be alarming. While you might initially think it’s just dirt, you could be dealing with black algae, one of the most persistent and challenging types of algae to plague swimming pools. Understanding what causes black algae and how to treat it is crucial for maintaining a clean, safe, and beautiful pool.
Aqua Leisure Pools & Spas will walk you through everything you need to know about these unwelcome protists. We’ll explain what black algae is, why it’s so difficult to remove, and what causes it to appear. Most importantly, we’ll provide a step-by-step plan to eliminate it from your pool and offer effective strategies to prevent black algae from returning.
Understanding Black Algae
Black algae is a common term for what is actually a type of bacteria called cyanobacteria. Unlike green or mustard algae that float freely in the water or cling loosely to surfaces, black algae embeds itself deeply into porous surfaces like plaster, concrete, and grout. It forms a protective, multi-layered biofilm that makes it highly resistant to normal chlorine levels and other sanitizers.
This protective layer is the primary reason black algae is so tough to eliminate. The outer layers shield the inner layers from chemicals, allowing the algae to survive and regrow even after a standard shock treatment. Its deep roots also mean that simply brushing the surface isn’t enough to kill it completely.
What Causes Black Algae?
Black algae doesn’t just appear out of nowhere. It’s typically introduced into the pool and thrives when conditions are just right.
Introduction of Spores
The most common way black algae enters a pool is through contamination. Spores can hitch a ride on swimwear or equipment that has been used in natural bodies of water like lakes, rivers, or the ocean. Even a nearby pond can be a source of spores carried by the wind.
Poor Water Chemistry
Imbalanced water chemistry creates an environment where algae can flourish.
- Low Chlorine: Inadequate chlorine levels are the number one invitation for algae growth. Without sufficient sanitizer, black algae can easily establish a foothold.
- High pH: When the pH level rises above 7.6, it significantly reduces the effectiveness of chlorine. This chemical imbalance allows algae to grow unchecked.
- High Phosphate Levels: Phosphates are a primary food source for all types of algae. High levels, often introduced through debris, certain pool chemicals, or even tap water, can fuel rapid algae growth.
Lack of Circulation and Filtration
Stagnant water is a breeding ground for bacteria and algae.
- Poor Circulation: If your pool pump doesn’t run long enough or if jets aren’t positioned correctly, certain areas can become dead spots with little to no water movement. These spots are prime real estate for black algae.
- Inefficient Filtration: A dirty or malfunctioning filter cannot effectively remove algae spores and other contaminants from the water, allowing them to accumulate and grow.
How to Identify Black Algae
Correctly identifying black algae is the first step toward effective treatment.
Visual Identification
Look for distinct black or dark bluish-green spots on your pool’s surfaces. These spots can range from the size of a pinhead to the size of a quarter. They typically appear on rougher surfaces, such as concrete or plaster, but can also form in tile grout and other crevices.
Textural Identification
If you scrape one of the spots with your fingernail and it feels slimy or has a gelatinous layer, you’re likely dealing with black algae. Unlike dirt or stains, it has a distinct biological texture due to its protective biofilm.
Your Complete Algae Removal Guide
Getting rid of black algae requires a more aggressive approach than other types of algae. Follow these steps carefully to reclaim your pool.
How to Remove Black Algae
- Brush the Algae Aggressively: The first and most critical step is to break down the algae’s protective layer. Use a stiff-bristle brush to scrub the black spots vigorously.
- For plaster or concrete pools, a steel-bristle brush is most effective.
- For vinyl or fiberglass pools, use a nylon-bristle brush to avoid scratching the surface.
- Balance Water Chemistry: Before shocking the pool, adjust your pH to between 7.2 and 7.6. This optimizes your chlorine’s killing power.
- Shock the Pool: After brushing, perform a heavy chlorine shock. You may need to use three or four times the normal dose to penetrate the algae’s remaining layers. Follow the manufacturer’s instructions and consider repeating the shock treatment over several days for severe infestations.
- Clean or Replace the Filter: Run your pump continuously for at least 24 hours after shocking. All the dead algae will need to be filtered out. Backwash your sand or D.E. filter, or clean your cartridge filter, to avoid reintroducing spores into the pool.
- Direct Treatment for Stubborn Spots: For any spots that remain, direct treatment is necessary. You can rub a chlorine tablet directly on the algae spot (wearing protective gloves, of course).
- Vacuum and Repeat Brushing: Once the algae appears dead (it will turn from black to a grayish color), vacuum the debris from the pool floor. Continue to brush the affected areas for several days to remove any lingering roots and prevent black algae from re-establishing itself.
How to Prevent Black Algae
Once the battle is won, the key is to ensure it never happens again. Prevention is far easier than treatment.
- Maintain Proper Water Chemistry: This is your best line of defense. Regularly test and maintain chlorine levels between 1-3 ppm and pH between 7.2-7.6. Keep alkalinity and cyanuric acid levels in their ideal ranges as well.
- Ensure Adequate Circulation: Run your pump and filter for at least 8-12 hours a day (or 24/7 if dealing with an outbreak). Ensure your jets are angled to create good circulation throughout the entire pool.
- Regularly Clean Pool Equipment: Routinely clean filters, skimmer baskets, and pump baskets. Also, brush the pool walls and floor weekly to dislodge any new spores before they can take root.
- Use Algaecides as a Preventive Measure: Adding a maintenance dose of a high-quality algaecide to your water on a weekly or bi-weekly basis can help prevent black algae growth.
- Monitor Phosphate Levels: Test for phosphates periodically and use a phosphate remover if levels get too high.
Your Dream Backyard Awaits
Dealing with black algae can be frustrating, but with the right knowledge and tools, you can restore your pool to its former glory. Consistent maintenance and balanced water chemistry are the cornerstones of a healthy, algae-free pool.
You have a vision of what you want your backyard to be — perhaps a beautiful oasis where the stresses of the day melt away as you float in your peaceful retreat. Whatever your dream, our experienced team at Aqua Leisure Pools and Spas will help it become a reality.
We know it is not just a swimming pool but a reflection of you and your style. Aqua Leisure is your one-stop shop providing pool and spa sales, installation, maintenance services, and a complete line of chemicals and accessories for any pool or spa. We offer quality work and attention to detail because our goal is customer satisfaction every time.
Contact us today and let our friendly sales staff help you find the in-ground swimming pool or spa of your dreams!
Posted by Aqua Leisure Pools & Spas in Pools