How to Handle Algae When Opening a Pool

When a pool sits unused and covered for months, algae can grow due to poor circulation, lack of sanitizer, and trapped debris. Understanding why it happens helps you prevent and address it properly.

Common Causes of Algae Growth

• Low chlorine or sanitizer levels

• Poor water circulation during the off-season

• Warm temperatures and sunlight under the cover

• Organic debris such as leaves and dirt

Assessing the Situation When You Open the Pool

Before jumping in to clean, it’s important to assess the type and extent of algae in your pool.

Types of Algae

• Green algae: The most common, floats in water or clings to walls.

• Yellow (mustard) algae: Powdery and sticks to shady areas.

• Black algae: Tough, stubborn spots that root into surfaces.

Initial Inspection

• Remove the pool cover and note water clarity.

• Check for visible algae on walls, floor, and steps.

• Test water chemistry to understand starting conditions.

Step-by-Step Guide to Handling Algae

Step 1: Remove Debris

• Use a leaf net to skim out large debris.

• Vacuum the pool bottom to remove settled dirt and leaves.

Step 2: Brush the Pool Surfaces

• Use a stiff pool brush to scrub walls, floor, and steps.

• Focus on areas with visible algae growth.

Step 3: Test and Balance Water

• Test pH, alkalinity, and chlorine levels.

• Adjust pH to around 7.2 for optimal chlorine effectiveness.

Step 4: Shock the Pool

• Add a high dose of chlorine shock to kill algae.

• Follow product directions for dosage based on pool size.

• Run the pump continuously for at least 24 hours.

Step 5: Brush and Vacuum Again

• Brush the surfaces again to loosen any remaining algae.

• Vacuum dead algae to waste so it does not circulate back.

Step 6: Run the Filter and Clean It

• Keep the filter running until water clears.

• Backwash or clean the filter after handling algae.

Tips for Preventing Algae After Opening

Maintain Proper Water Chemistry

• Keep chlorine levels within the recommended range.

• Test water two or three times a week.

Improve Circulation

• Ensure all jets and returns are working properly.

• Run the pump for sufficient hours each day.

Regular Brushing and Cleaning

• Brush surfaces weekly to prevent algae attachment.

• Skim debris daily to keep water clean.

Advanced Tips for Experienced Owners

1. Use an algaecide after shocking to help prevent regrowth.

2. Upgrade to a high-efficiency filter to remove fine particles.

3. Inspect pool equipment during opening for optimal performance.

4. Install a timer to ensure consistent circulation.

Common Mistakes to Avoid

• Not brushing the pool thoroughly, which leaves algae in place.

• Underestimating the amount of shock needed.

• Failing to clean the filter after treating algae.

• Letting the water sit too long after uncovering before starting maintenance.

By following these steps, you can handle algae when opening your pool and enjoy a clean, inviting swim. Regular maintenance and prompt action keep algae at bay all season long.