Pool Algae Types Explained: Green, Black, Yellow Algae
Complete guide to identifying and treating different types of pool algae in Australia. Learn how to remove green, black, and yellow algae.
Types of Pool Algae
There are three main types of pool algae, each requiring different treatment approaches:
🟢 Green Algae (Most Common)
Appearance:
- Green water or green spots on walls/floor
- Slimy texture
- Can make pool water cloudy
- Easiest to treat
Causes:
- Low or no chlorine
- Poor circulation
- Imbalanced chemistry
- Warm water temperatures
Treatment:
- Balance pH (7.2-7.6) and alkalinity (80-120 ppm)
- Shock pool with 3-5x normal chlorine dose
- Brush all surfaces daily
- Run pump 24 hours until clear
- Clean filter frequently
- Maintain chlorine at 1-3 ppm
Use PoolCalculator.com.au to calculate exact shock dosage.
âš« Black Algae (Most Difficult)
Appearance:
- Dark black or blue-green spots
- Rough, raised texture
- Deep roots in pool surface
- Very difficult to remove
Causes:
- Very low chlorine levels
- Poor maintenance
- Rough pool surfaces (provides attachment points)
- Warm, stagnant water
Treatment:
- Balance chemistry first (pH 7.2-7.6, TA 80-120)
- Brush aggressively with steel brush to break protective layer
- Shock with very high chlorine (5-10x normal dose)
- Apply algaecide directly to spots
- Continue brushing daily for 1-2 weeks
- Maintain high chlorine levels
- May require professional treatment
Warning: Black algae has deep roots and protective coating. Aggressive, persistent treatment is required.
🟡 Yellow/Mustard Algae
Appearance:
- Yellowish-brown or mustard color
- Often in shaded areas
- Powdery texture
- Resistant to normal chlorine
Causes:
- Low chlorine levels
- Shaded areas (less UV exposure)
- Resistant to normal chlorine levels
- Often appears after green algae treatment
Treatment:
- Balance chemistry
- Shock pool with high chlorine dose
- Use specialized yellow algae algaecide
- Brush all surfaces thoroughly
- Run pump continuously
- Maintain higher chlorine levels (2-4 ppm)
- Treat shaded areas specifically
What Causes Pool Algae?
Algae spores are always present in the air and water. They only grow when conditions are favorable:
- Low or no chlorine - Primary cause
- Poor circulation/filtration - Stagnant water
- Imbalanced chemistry - Especially pH and alkalinity
- Warm water temperatures - Algae thrives in warm water
- High phosphates - Algae food source
- Lack of maintenance - Infrequent cleaning/testing
Prevention Tips
Regular Maintenance:
- Test water weekly
- Maintain chlorine 1-3 ppm
- Balance pH and alkalinity
- Clean filter regularly
Proper Circulation:
- Run pump 8-12 hours daily
- Ensure proper water flow
- Clean skimmer baskets
- Brush pool weekly
Calculate Your Algae Treatment
Use our free calculator to determine exact shock dosage for treating algae.
Use Pool Calculator →Quick Reference
| Algae Type | Difficulty | Shock Dosage | Treatment Time |
|---|---|---|---|
| Green Algae | Easy | 3-5x normal | 2-3 days |
| Black Algae | Very Difficult | 5-10x normal | 1-2 weeks |
| Yellow Algae | Moderate | 4-6x normal + algaecide | 3-5 days |