Introduction
Algae are every pool owner's nightmare in summer. In just a few days, a crystal clear pool can transform into a green swamp. Intense heat, prolonged sunlight and frequent use create perfect conditions for these organisms to proliferate.
In Margem Sul, with hot and dry summers, the challenge is even greater. Water temperatures above 28°C are common, and in these conditions algae can double in just 24 hours.
This guide presents preventive and curative strategies to keep your pool algae-free throughout summer.
Know the Enemy: Types of Algae
Green Algae (Chlorophyta)
| Characteristic | Description |
|---|
| Appearance | Cloudy green water or wall stains |
| Location | Surface, walls, corners |
| Speed | Very fast to proliferate |
| Difficulty | Easy to eliminate |
Yellow/Mustard Algae (Xanthophyta)
| Characteristic | Description |
|---|
| Appearance | Yellowish powder, sand-like |
| Location | Walls, especially shadows |
| Speed | Moderate |
| Difficulty | More resistant, require specific treatment |
Black/Blue Algae (Cyanobacteria)
| Characteristic | Description |
|---|
| Appearance | Rooted dark spots |
| Location | Joints, concrete, rough surfaces |
| Speed | Slow but persistent |
| Difficulty | Very difficult, require aggressive treatment |
Pink Algae (Bacteria)
| Characteristic | Description |
|---|
| Appearance | Pink/reddish stains |
| Location | Waterline, skimmers, corners |
| Speed | Moderate |
| Difficulty | Medium, responds well to chlorine |
💡 Dica Profissional
Most algae appearing in Margem Sul pools are green. If you identify yellow or black algae, prepare for more intensive and prolonged treatment.
Why Algae Appear
Risk Factors
| Factor | Impact |
|---|
| Insufficient chlorine | Main cause |
| High pH | Less effective chlorine |
| High temperature | Accelerates growth |
| Intense sunlight | Feeds photosynthesis |
| Insufficient filtration | Allows accumulation |
| High organic load | Nutrients for algae |
| Standing water | Zones without circulation |
Dangerous Combinations
| Situation | Risk |
|---|
| Heat + Low chlorine | Algae in 24-48h |
| Party + No treatment | Algae in 2-3 days |
| Holiday without maintenance | Guaranteed algae |
| Rain + No adjustment | Algae in 3-5 days |
Highest Risk Zones
| Zone | Why |
|---|
| Corners | Less circulation |
| Ladders | Rough surfaces, shade |
| Behind ladders | Dead zone |
| Waterline | Nutrients, less chlorine |
| Floor (corners) | Accumulated sediment |
Prevention Strategy
The 4 Cs Rule
| C | Meaning | Objective |
|---|
| Chlorine | Adequate level | 1-3 ppm constant |
| Circulation | Water in movement | 8-12h filtration/day |
| Care | Regular cleaning | Remove nutrients |
| Consistency | Daily routine | Don't skip |
Ideal Summer Levels
| Parameter | Value |
|---|
| Free chlorine | 2-3 ppm (slightly high) |
| pH | 7.2-7.4 |
| Stabiliser | 30-50 ppm |
| Alkalinity | 80-120 ppm |
Testing Frequency
| Test | Summer Frequency |
|---|
| Chlorine | Daily |
| pH | Daily |
| Alkalinity | 2x week |
| Stabiliser | Weekly |
Effective Chlorination
Maintaining Constant Chlorine
| Method | Advantage |
|---|
| Tablets in dispenser | Constant release |
| Electrochlorinator (salt) | Automatic |
| Daily manual addition | Total control |
| Dosing pump | Precision |
Preventive Shock Treatment
| Frequency | Dose | When |
|---|
| Weekly | 10-15 g/m³ | Friday or Saturday night |
| After intensive use | 15-20 g/m³ | Same night |
| After rain | 10-15 g/m³ | Immediately |
| First signs | 20-30 g/m³ | Urgent |
Super-Chlorination
| Indication | Procedure |
|---|
| Monthly preventive | Raise to 10 ppm, let drop |
| Slightly cloudy water | Raise to 15 ppm |
| Very slight green | Raise to 20 ppm |
💡 Dica Profissional
Weekly shock is the best prevention. Always do it at night to avoid UV loss. A Friday night shock prepares the pool for the weekend.
Using Algaecides
Types of Algaecides
| Type | Function | Use |
|---|
| Quaternary | Basic prevention | Weekly, economical |
| Polymeric | Long lasting | Fortnightly |
| Copper-based | Very effective | Beware of staining |
| Peroxide | Oxidising | Specific treatment |
When to Use Algaecide
| Situation | Recommended Type |
|---|
| Normal prevention | Weekly quaternary |
| Holidays | Polymeric/long lasting |
| History of algae | Quaternary + shock |
| Resistant algae | Copper-based (carefully) |
Typical Dosage
| Product | Prevention Dose | Treatment Dose |
|---|
| Standard algaecide | 0.5-1 L/50m³ | 1-2 L/50m³ |
| Concentrated algaecide | 0.25-0.5 L/50m³ | 0.5-1 L/50m³ |
| Long-lasting algaecide | Per label | Per label |
Optimised Filtration
Summer Filtration Time
| Water Temperature | Minimum Time |
|---|
| 25-27°C | 10-12 hours |
| 28-30°C | 12-14 hours |
| 31-33°C | 14-16 hours |
| >33°C | 16-20 hours |
Strategic Schedules
| Period | Benefit |
|---|
| 8am-2pm | Morning, peak solar |
| 4pm-10pm | Afternoon, after use |
| 2h during early morning | Break overnight stagnation |
Filter Maintenance
| Task | Frequency |
|---|
| Check pressure | Daily |
| Backwash | When +0.3 bar |
| Clean pre-filter basket | Daily |
| Check return jets | Weekly |
Physical Cleaning
Anti-Algae Routine
| Task | Frequency | Objective |
|---|
| Brush walls | 2-3x week | Loosen spores |
| Brush ladders | 2-3x week | Risk zone |
| Brush corners | 2-3x week | Dead zones |
| Vacuum floor | 2x week | Remove debris |
| Clean waterline | Weekly | Remove oils |
Critical Points
| Zone | Special Attention |
|---|
| Behind ladders | Brush vigorously |
| Tile joints | Brush with hard brush |
| Floor corners | Vacuum well |
| Return jets | Check direction |
| Skimmers | Clean regularly |
Water Circulation
Eliminate Dead Zones
| Problem | Solution |
|---|
| Corner without circulation | Adjust jets |
| Stagnant water | Increase filtration time |
| Standing surface | Check skimmers |
| Floor without movement | Pool robot |
Jet Adjustment
| Direction | Objective |
|---|
| Slightly downward | Circulate floor |
| At angle | Create rotation |
| Avoid pointing at walls | Prevent dead zones |
Daily Prevention Checklist
Morning
- [ ] Test chlorine (adjust if <2 ppm)
- [ ] Test pH (adjust if outside 7.2-7.4)
- [ ] Observe water colour
- [ ] Check walls (stains?)
- [ ] Start filtration if not automatic
End of Day
- [ ] Collect leaves and debris
- [ ] Check skimmers
- [ ] Add chlorine if needed
- [ ] Check pump programming
Weekly
- [ ] Shock treatment (Friday/Saturday)
- [ ] Add algaecide
- [ ] Brush all surfaces
- [ ] Backwash if needed
- [ ] Check jets
First Signs of Algae
Early Identification
| Sign | Meaning |
|---|
| Slightly greenish water | Start of green algae |
| Slippery walls | Biofilm forming |
| Chlorine drops quickly | Algae consuming |
| Corners with slime | Algae establishing |
| "Pond" smell | Advanced growth |
Immediate Action
| Step | Procedure |
|---|
| 1 | Test water (pH, chlorine) |
| 2 | Adjust pH to 7.2 |
| 3 | Brush all surfaces |
| 4 | Double shock treatment |
| 5 | Add algaecide |
| 6 | Filter 24h continuous |
| 7 | Check next day |
💡 Dica Profissional
Speed of action is crucial. Algae treated in the first 24 hours resolve in 1-2 days. Algae ignored for a week can take 1-2 weeks to resolve.
Treating Established Algae
Light Green Algae
| Step | Procedure |
|---|
| 1 | Adjust pH to 7.2 |
| 2 | Brush vigorously |
| 3 | Shock 20-30 g/m³ |
| 4 | Algaecide treatment dose |
| 5 | Filter 24-48h |
| 6 | Vacuum to waste |
Moderate Green Algae
| Step | Procedure |
|---|
| 1 | Adjust pH to 7.0 |
| 2 | Brush intensively |
| 3 | Triple shock (30-40 g/m³) |
| 4 | Double algaecide dose |
| 5 | Flocculant |
| 6 | Filter 48h continuous |
| 7 | Vacuum to waste |
| 8 | Repeat if necessary |
Severe Green Algae
| Step | Procedure |
|---|
| 1 | Consider partial draining |
| 2 | pH to 7.0 |
| 3 | Brush with steel brush (if concrete) |
| 4 | Very strong shock (50+ g/m³) |
| 5 | Maximum algaecide |
| 6 | Flocculant |
| 7 | Filter continuous |
| 8 | Vacuum to waste |
| 9 | Repeat 2-3 times |
Resistant Algae (Yellow/Black)
| Treatment | Specificity |
|---|
| Yellow algae | Specific algaecide + triple shock |
| Black algae | Direct granular chlorine + brushing |
| Pink bacteria | Shock + quaternary algaecide |
Common Mistakes to Avoid
| Mistake | Consequence | Correction |
|---|
| Chlorine only at weekends | Algae during week | Daily chlorination |
| Not brushing | Algae grow protected | Brush 2-3x/week |
| Ignoring first signs | Problem worsens | Immediate action |
| Only algaecide (no chlorine) | Ineffective | Always combine |
| Filtering little | Dead zones | Increase time |
| Trusting "clean" water | Invisible algae | Test regularly |
Margem Sul Specific Factors
Regional Challenges
| Challenge | Solution |
|---|
| Intense heat (35°C+) | Increase chlorine and filtration |
| Hard water (calcareous) | Monitor pH frequently |
| Pine trees (needles) | Clean more frequently |
| Wind (dust) | Cover when not using |
| Rural areas (agricultural dust) | Increase flocculation |
Risk Calendar
| Month | Risk Level | Action |
|---|
| June | Medium-High | Start rigorous routine |
| July | Very High | Maximum vigilance |
| August | Very High | Maximum vigilance |
| September | High | Maintain routine |
Frequently Asked Questions
Why do algae appear even with chlorine?
Chlorine may seem sufficient but be rapidly consumed by organic matter or invisible algae. It may also be inactive due to high pH or excess stabiliser.
Can I swim in slightly green water?
Not recommended. Even slightly green water indicates presence of algae and possible bacteria. Treat first, swim later.
Do algaecides replace chlorine?
No. Algaecides are complementary to chlorine, not substitutes. A pool needs chlorine for sanitation and can use algaecide for extra prevention.
How long does it take to eliminate algae?
Depends on severity: light algae take 1-2 days, moderate 3-5 days, severe 1-2 weeks. Quick action is fundamental.
Why do algae return after treatment?
Usually because they weren't completely eliminated, chlorine wasn't maintained, or spores survived in the filter. After treatment, keep chlorine high and clean the filter.
Conclusion
Preventing algae in summer is a constant but winnable battle:
- Maintain chlorine between 2-3 ppm always
- Brush walls and corners regularly
- Filter enough time for the temperature
- Treat with weekly preventive shock
- Act quickly at first signs
- Combine chlorine with algaecide for maximum protection
An algae-free pool requires daily attention, but the effort is worth it for crystal clear water all summer.
If you need professional help fighting or preventing algae in your pool in Margem Sul, ManutençãoPiscinas is here to help. Contact us for a no-obligation quote.
