Will phosphate remover clear a green pool? It is one of the most common questions at the pool supply counter, and the honest answer is no, not on its own. Phosphate remover takes away some of the food algae lives on. It does not kill the algae already turning your water green. To understand what will work, it helps to know why pools in Phoenix go green in the first place, and why the Valley's sun and heat make it happen faster than people expect.
A quick note on who is writing this. Phoenix Pool Cleaning Pro is a free phone line, not a pool company. It connects callers with independent local pool service companies, which see the pool, quote and do the work. This guide is general information drawn from the public health and university sources listed at the bottom of the page. It does not give chemical doses, and it is not a substitute for someone testing your water.
The short version: green water means algae is growing faster than the chlorine can kill it. Fix the chlorine, the pH, the stabilizer and the circulation, and remove the algae with brushing and filtering. Phosphate removers and clarifiers are supporting players, not the cure.
Why pools turn green in the desert
Algae spores blow into every pool, all the time. A healthy pool kills them before they settle in. A pool turns green when something tips that balance. Michigan State University's pool operator manual lists sunlight, temperature, pH, chlorine level and mineral content among the factors that decide whether algae takes hold and how fast it grows. Phoenix pushes several of those at once.
The sun burns chlorine off
Free chlorine is what kills algae and germs, and sunlight breaks it down. The CDC lists sunlight among the things that reduce chlorine in a home pool and says chlorine has to be tested routinely because so much can lower it. Under a summer sun in the Valley, a level that looked fine in the morning can be gone by late afternoon, and algae needs only a gap of a day or two.
Stabilizer is too low, or too high
Cyanuric acid, usually sold as stabilizer or conditioner, attaches loosely to chlorine and shields it from ultraviolet light. Too little, and the sun strips the chlorine away. Too much, and the chlorine is held so tightly it works slowly: the CDC notes that cyanuric acid decreases how well chlorine disinfects. Stabilizer does not evaporate, so it tends to build up over a season.
Heat speeds the algae up
Warm water is friendlier to algae. In a Phoenix July, pool water can sit warm for weeks, and every day of warm water with low chlorine gives algae a head start. That is why a pool that stays clear with a little attention in March can go green quickly in summer.
The pH has drifted
Chlorine works best in a fairly narrow pH range. The MSU manual explains that a high pH reduces how well chlorine kills and encourages algae growth. The CDC's range for home pools is a pH of 7.0 to 7.8.
Phosphates are feeding it
Phosphate is a nutrient. Algae uses it to grow, so a pool with a lot of phosphate gives any algae that survives the chlorine more to work with. High phosphate does not turn a well-chlorinated pool green by itself, but it makes a pool that is already struggling harder to keep clear.
The water is not moving enough
Chlorine only works where the water carries it. If the pump runs too few hours, the timer was knocked off its schedule, or a clogged filter cuts the flow, corners and steps become dead spots where algae starts. Still, green water is also where mosquitoes breed, which is why Maricopa County's mosquito prevention advice covers pools. The guide to cleaning a pool filter explains how a dirty filter slows everything down.
Monsoon storms add a load all at once
The National Weather Service treats June 15 through September 30 as Arizona's monsoon season. A dust storm or a downpour can dump dirt, leaves and debris into the pool in an hour and knock the power out to the equipment. All of that uses up chlorine and gives algae somewhere to grow. The monsoon pool care guide covers what to do after a storm.
Green, yellow or black: what the color tells you
The MSU manual describes three common types of pool algae, usually named for their color. They do not all respond the same way, which is why a fix that works on one pool fails on another.
Green algae
Turns the water itself green, from a light tint to a swamp. The MSU manual describes it as very responsive to chemical treatment, so it is the type that responds best to proper chlorination, brushing and filtering.
Yellow (mustard) algae
Shows up as yellow patches on the walls and steps. It clings more tightly than green algae and resists chemicals better, though the manual notes it can be brushed off. It needs brushing and treatment together.
Black algae
Dark spots on the pool surface. The manual says black algae has a tough outer layer that resists chemicals and needs a stainless steel brush. This one is usually worth a professional from the start.
Will phosphate remover clear a green pool? What it really does
Phosphate removers are sold to bind dissolved phosphate into a solid that the filter can trap. That is the job they are designed for. They are not sanitizers or algaecides, so the algae already in the water is still alive and still green after a dose. Industry guides on phosphates make the same point.
That is why the usual order is to kill and remove the algae first, then use a remover afterward only if testing shows phosphate is high, to make regrowth harder.
What phosphate remover can do
- Lower the dissolved phosphate in water that tests high
- Make it harder for algae to regrow once the pool is clear
- Support, not replace, steady chlorine and good circulation
What it cannot do
- Kill algae that is already growing
- Make up for low chlorine, high pH or too much stabilizer
- Fix a pump that runs too little or a clogged filter
One practical side effect: the solid a remover forms ends up in the filter. If you or your pool company use one, expect to check the filter pressure and clean the filter afterward.
What a pool clarifier does, and what it does not
A clarifier is for cloudy water, not green water. Pool water often holds particles too small for the filter to catch: dust, pollen, bits of dead algae and other fine debris. A clarifier makes those tiny particles stick together into clumps big enough for the filter to trap. In other words, the clarifier does not remove anything itself. The filter does, so the pump has to run and the filter has to be clean for a clarifier to help.
Flocculants are a different product with a different job. If a company suggests one, ask why it fits your pool and what the cleanup afterward involves.
Will pool clarifier remove phosphates?
No, not in a dependable way. Phosphate in pool water is dissolved, like sugar in tea, not a particle floating around. A clarifier works on particles. Some products combine a clarifier with a phosphate treatment and are labeled that way, but a plain clarifier is not made to pull dissolved phosphate out.
Will pool clarifier remove pollen?
It can help with the haze. Pollen grains are among the fine particles that can slip through a filter, and a clarifier helps the filter catch them. It does nothing about the next round of pollen blowing in, so skimming the surface, emptying the skimmer and pump baskets, and cutting back plants that drop into the pool do most of the work.
Keeping a Phoenix pool from turning green again
- Test often in summer. Use a home test kit for chlorine and pH. The CDC says chlorine must be tested routinely, and Valley heat and sun use it up fast in summer.
- Have stabilizer checked. Ask a pool company to measure cyanuric acid now and then and tell you if it has built up too far.
- Keep the water moving. Check that the timer or automation still runs the pump on schedule, especially after a power outage or monsoon storm.
- Watch the filter gauge. A pressure reading well above the clean reading means the filter needs cleaning. See pool filter cleaning.
- Brush and skim. Brushing the walls and steps breaks up algae before it settles in. Skim after dust storms.
- Store chemicals safely. Never mix pool chemicals with each other. Keep them in their original containers, apart, dry, shaded and out of children's reach, and follow the label.
When to call a pool company instead
If the pool has turned from tint to solid green, if you cannot see the drain at the bottom of the deep end, or if black or mustard algae keeps coming back, it is time for a professional. Clearing a green pool takes heavy chlorination that should not be done by guesswork, and a pool company can also find the cause, whether it is stabilizer, equipment or circulation. The green pool cleanup page explains what that job involves, and weekly cleaning and maintenance covers keeping it clear afterward.
Murky water is a drowning hazard. Keep children and pets away from a green or cloudy pool, and keep gates latched. Nobody should swim until the bottom is clearly visible and the water has been tested.
Pool turning green, cloudy or spotted? Call the line, describe what you see, and you will be put through to a local pool service company that can test the water and give you its own price.
- Call the numberAn automated assistant answers (623) 240-0428 day or night, weekends included.
- Describe the poolSay what is going on: cloudy or green water, a pump that hums, a heater that will not fire, scale on the tile, and which part of the Valley you are in.
- Get put throughThe call is transferred to an independent, locally owned pool service company, which hears a short summary of the problem before it picks up.
- Deal with them directlyThat company looks at the pool, quotes, does the work and bills you. If it cannot answer, your name, number, area and problem are passed along so it can call you back.
About this line: Phoenix Pool Cleaning Pro is a free phone line, not a pool company. It answers your call and connects you with an independent local pool service company, which inspects, quotes and does the work, and which you pay directly. Companies may pay a referral fee. You never pay the line. See how the line works.