10/28/2026
S&S POOLS – POOL SCHOOL: WEEK 7 💦
🧪 PHOSPHATES: THE HIDDEN NUTRIENT THAT CAN FEED ALGAE IN YOUR POOL! 🧪
Have you ever wondered why algae keeps returning to your swimming pool, even after treatment?
One factor worth investigating is PHOSPHATES!
This week, we’re explaining what phosphates are, how they enter your pool, why they matter, and how to control them.
🌿 WHAT ARE PHOSPHATES?
Phosphates are naturally occurring compounds containing phosphorus. They can enter your swimming pool through several sources, including:
🍃 Leaves, grass clippings, pollen, and other organic debris
🌧️ Rainwater, soil, and runoff
🌱 Lawn fertilizers and landscaping products
💦 Fill water from certain municipal or well-water sources
🧴 Some pool chemicals and treatment products
Phosphates themselves do not automatically turn your pool green or cloudy. However, they provide an important nutrient that algae can use to grow.
⚠️ WHY ARE HIGH PHOSPHATES A CONCERN?
Algae need nutrients, sunlight, and suitable growing conditions to thrive.
When phosphate levels are elevated, algae have access to an additional food source.
If your free chlorine level drops too low, algae may begin multiplying rapidly.
High phosphates can contribute to:
❌ Faster algae growth when sanitizer levels are inadequate
❌ Recurring algae problems
❌ Increased difficulty maintaining clear water during algae outbreaks
❌ Additional chlorine consumption when algae and other contaminants are present
IMPORTANT: Phosphates do not directly consume chlorine. Algae and other contaminants create chlorine demand. A properly chlorinated pool can remain clear even when phosphate levels are elevated.
🔬 WHAT SHOULD YOUR PHOSPHATE LEVEL BE?
Phosphates are typically measured in parts per billion (ppb) rather than parts per million (ppm).
Here is a general guide to phosphate levels:
💧 0–100 ppb: Very low phosphate levels.
💧 100–300 ppb: Relatively low levels.
💧 300–500 ppb: Moderate levels. Some pool professionals may recommend monitoring.
💧 500–1,000 ppb: Elevated levels. Phosphate removal may be considered, particularly with recurring algae problems.
💧 Above 1,000 ppb: High levels. Further investigation and possible treatment may be beneficial.
These are general phosphate-management ranges, not universal pool water standards. There is no single phosphate concentration at which algae automatically begins growing.
🧪 CAN YOUR POOL HAVE HIGH PHOSPHATES AND STILL LOOK CLEAR?
ABSOLUTELY!
A swimming pool can have elevated phosphate levels and still maintain crystal-clear water.
Why?
Because properly maintained free chlorine prevents algae from growing, even when nutrients are available.
This is why FREE CHLORINE IS YOUR MOST IMPORTANT DEFENSE AGAINST ALGAE!
Phosphate management is an additional preventive measure, not a replacement for proper water chemistry.
🛠️ HOW DO YOU REMOVE PHOSPHATES?
When phosphate removal is appropriate, pool professionals commonly use a specialized phosphate-removing product.
Many phosphate removers contain lanthanum compounds that react with dissolved phosphates, forming particles that can be captured by the filtration system.
During treatment, you may notice:
💦 Temporary cloudy or milky water
💦 Increased filter pressure as particles are collected
💦 A need for additional filter cleaning or backwashing
💦 Gradual improvement in water clarity as filtration removes the particles
Always follow the specific phosphate remover’s instructions. Treatment amounts, circulation requirements, and filter maintenance vary by product.
🚨 DOES PHOSPHATE REMOVER KILL ALGAE?
NO!
This is one of the biggest misconceptions in swimming pool maintenance.
Phosphate remover does not kill existing algae. It removes a nutrient algae need to grow.
If your pool already has an algae outbreak, the algae must be treated through proper sanitization, brushing, filtration, and water chemistry management.
Removing phosphates alone will not eliminate an active algae bloom.
💡 WHY DO PHOSPHATES SOMETIMES KEEP COMING BACK?
Even after treatment, phosphate levels can rise again because new phosphates continuously enter your swimming pool.
Common reasons include:
🍂 Trees and landscaping surrounding the pool
🌧️ Heavy rainfall and runoff
🌾 Nearby lawn fertilization
💦 Phosphates already present in the fill water
🧴 Certain pool treatment products
Routine maintenance, proper filtration, and removing organic debris can help limit phosphate accumulation.
⭐ S&S POOLS PROFESSIONAL TIP OF THE WEEK!
Before assuming phosphates are responsible for an algae problem, always evaluate the complete water chemistry.
Your pool’s:
✅ Free Chlorine (FC)
✅ Total Chlorine (TC)
✅ pH
✅ Total Alkalinity (TA)
✅ Calcium Hardness (CH)
✅ Cyanuric Acid (CYA)
All play important roles in maintaining healthy pool water.
Remember, your free chlorine level must be appropriate for your stabilizer (CYA) level.
THE BOTTOM LINE:
💙 Phosphates feed algae, but they do not cause algae to grow when proper sanitization prevents it.
💙 High phosphates do not automatically mean your pool has a problem.
💙 Phosphate removers can be useful preventive tools, especially in pools experiencing recurring algae issues.
💙 Proper chlorine levels, balanced water chemistry, circulation, and filtration should ALWAYS come first!
🌊 AT S&S POOLS, WE BELIEVE AN EDUCATED POOL OWNER IS A HAPPY POOL OWNER!
Stay tuned for more weekly pool care education from S&S Pools!