The Biology of Algae: Why We Scrub It Before We Treat It
When a pool turns green, most people think the solution is simple:
“Just add more chlorine.”
But algae isn’t just green water.
It’s a living organism — and understanding its biology explains why we always scrub first, treat second.
What Is Pool Algae, Really?
Algae are microscopic, plant-like organisms that thrive in:
Warm water
Sunlight
Poor circulation
Low or ineffective chlorine
Nutrient-rich environments (phosphates, debris, organics)
Algae spores are constantly present in the environment. Wind, rain, swimmers and even dust introduce them into your pool regularly.
They’re always there.
They only bloom when conditions allow.
How Algae Grows in Your Pool
Algae reproduce rapidly through cell division.
In warm Australian conditions, that reproduction rate increases dramatically. Once chlorine levels drop or become ineffective, algae:
Attach to pool surfaces
Begin forming microscopic colonies
Develop protective outer layers
Multiply quickly
What starts as invisible spores can become visible cloudiness or green walls in just days.
The Protective Layer You Can’t See
Here’s where biology becomes important.
As algae colonies grow, they produce a protective barrier often referred to as a biofilm.
A biofilm:
Shields algae from sanitiser
Reduces chemical penetration
Allows colonies to anchor to surfaces
Makes treatment harder
Simply pouring chlorine into the water doesn’t automatically break through that barrier.
That’s why scrubbing matters.
Why We Physically Scrub Before Treatment
When we brush and scrub pool walls and floors, we:
Break apart biofilms
Dislodge algae colonies from surfaces
Expose algae cells directly to sanitiser
Prevent regrowth from anchored spores
Improve circulation in affected areas
Scrubbing turns algae from a protected surface colony into suspended particles that chlorine can properly oxidise and destroy.
Without agitation, chemicals often struggle to fully penetrate established growth.
Why “Shock First” Often Fails
If a pool owner adds high levels of chlorine without brushing:
Surface algae may survive
Black spot algae remains embedded
Mustard algae clings to shaded areas
The pool may temporarily clear, then return
Treatment without mechanical disruption can lead to repeated outbreaks.
The Three-Part Approach to Proper Algae Recovery
Professional recovery involves:
Physical agitation (brushing & vacuuming)
Chemical oxidation (correct sanitiser levels)
Filtration and debris removal
It’s a biological and chemical process — not just a chemical one.
Why Early Action Matters
The longer algae is allowed to establish:
The thicker biofilm becomes
The more chlorine is required
The greater the strain on equipment
The higher the recovery cost
Early intervention reduces both time and expense.
The Bottom Line
Algae isn’t just discoloured water.
It’s a living organism protecting itself.
That’s why we don’t just treat pools — we disrupt the biology first.
Scrubbing isn’t extra effort.
It’s science.