How to Prevent & Get Rid of

Algae in Your Pool

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Nothing ruins a swimming pool faster than algae. What starts as a slight green tint can quickly turn into cloudy, slimy water that makes your pool look uninviting and unsafe for swimming.  The good news is that algae is usually preventable with regular maintenance and proper water chemistry. If algae does appear, taking quick action can help restore your pool to crystal-clear condition.  Here's everything you need to know about preventing, identifying, and treating pool algae.

 

What Is Pool Algae?

Pool algae are microscopic plant-like organisms that thrive in warm water, sunlight, and poorly maintained pools. Algae spores are everywhere—in the air, rain, wind, and even on swimsuits and pool toys—so every pool is exposed to them.  When chlorine levels drop or water circulation is poor, algae can begin growing rapidly.

 

Types of Pool Algae

 

Green Algae

Green algae is the most common type found in swimming pools.

 

Signs include:

• Green or cloudy water

• Slippery walls and steps

• Green patches on the pool floor

• Water that becomes cloudy before turning green

 

Green algae can usually be eliminated with proper brushing, shocking, and filtration.

 

Yellow (Mustard) Algae

• Mustard algae often appears as yellow or brown dust on shaded walls and the pool floor.

• Unlike dirt or pollen, it returns quickly after being brushed away.

• Mustard algae is more resistant to chlorine than green algae and often requires specialized treatment.

 

Black Algae

• Black algae appears as dark blue-black spots that grow into the pool surface.

• It is most common in concrete, plaster, and gunite pools because its roots can penetrate tiny surface pores.

• Black algae is the most difficult type to remove and usually requires aggressive brushing and repeated chemical treatment.

 

What Causes Pool Algae?

Several conditions can encourage algae growth.

 

Low Chlorine

Chlorine is your pool's primary defense against algae. When chlorine levels fall below the recommended range, algae can begin growing quickly.

 

Poor Water Circulation

Areas with little water movement become breeding grounds for algae.

Common circulation problems include:

• Pump not running long enough

• Dirty filter

• Blocked return jets

• Dead spots behind ladders and steps

• Clogged skimmer baskets

 

Unbalanced Water Chemistry

Improper pH and alkalinity reduce chlorine's effectiveness.

Recommended ranges:

• Free Chlorine: 1–3 ppm

• pH: 7.2–7.6

• Total Alkalinity: 80–120 ppm

• Cyanuric Acid: 30–50 ppm

 

Dirty Pool

Leaves, grass, insects, pollen, and other debris provide nutrients that algae can feed on.

Pools left uncovered for long periods are especially vulnerable.

 

Hot Weather

Warm temperatures and direct sunlight create ideal growing conditions for algae, especially during the hottest months of summer.

 

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How to Prevent Pool Algae

 

Preventing algae is much easier—and less expensive—than treating it.

 

Test Your Water Regularly

Check your pool chemistry at least two to three times per week during the swimming season.

Keeping chlorine and pH within the proper range is the best defense against algae.

 

Keep Your Pool Clean

Make it part of your weekly routine to:

• Skim leaves and debris

• Vacuum the pool

• Brush walls and steps

• Empty skimmer baskets

• Clean pump baskets

Organic debris can quickly lead to algae growth if left in the pool.

 

Run Your Filtration System Daily

Your pump should generally run 8–12 hours per day, depending on pool size, weather, and usage.

During periods of heavy use or hot weather, longer run times may be beneficial.

 

Clean Your Filter

Whether you have a sand, cartridge, or DE filter, regular cleaning is essential.

A clogged filter cannot effectively remove algae spores and fine debris.

 

Brush Your Pool Weekly

Brushing removes algae spores before they have a chance to establish themselves.

Pay special attention to:

• Corners

• Steps

• Behind ladders

• Waterline tile

• Shaded areas

 

Shock Your Pool When Needed

Shocking helps eliminate contaminants that regular chlorine may not fully remove.

Consider shocking your pool:

• After heavy rain

• Following a pool party

• During extremely hot weather

• If chlorine levels drop

• At the first sign of cloudy water

Always follow the manufacturer's directions when adding shock.

 

Use an Algaecide

Many pool owners use a preventive algaecide as part of their regular maintenance routine.

While not a substitute for proper chlorine levels, it can provide additional protection during peak swimming season.

 

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How to Get Rid of Pool Algae

 

If algae has already appeared, don't panic. Follow these steps:

 

Step 1: Test the Water

Begin by testing:

• Free chlorine

• pH

• Total alkalinity

• Stabilizer (cyanuric acid)

Balanced water helps treatments work more effectively.

 

Step 2: Brush the Entire Pool

Aggressively brush:

• Walls

• Floor

• Steps

• Corners

• Around ladders

• Behind return fittings

Brushing breaks algae loose so chlorine can kill it more effectively.

 

Step 3: Shock the Pool

Use a pool shock product according to the manufacturer's instructions.

For severe algae problems, multiple treatments may be required.

Allow the pump to circulate continuously after shocking.

 

Step 4: Run the Filter Continuously

Keep the filtration system running 24 hours a day until the water clears.

This helps remove dead algae and suspended particles.

 

Step 5: Vacuum the Pool

Once algae settles to the bottom:

• Vacuum thoroughly.

• Empty baskets frequently.

• Backwash or clean the filter as needed.

 

Step 6: Retest and Rebalance

Once the water clears:

• Test all chemical levels again.

• Adjust pH, alkalinity, and chlorine.

• Resume your regular maintenance schedule.

 

 

When Should You Avoid Swimming?

Do not swim if:

• The water is green.

• You cannot clearly see the bottom of the pool.

• Chlorine or pH levels are outside safe swimming ranges.

• Algae is actively growing.

Clear water isn't just about appearance—it's also an important safety issue.  Can algae damage your pool?  Yes.

 

If left untreated, algae can:

• Stain pool surfaces

• Clog filters

• Reduce water circulation

• Increase chemical costs

• Damage pool finishes

• Create slippery surfaces that increase the risk of falls

 

The sooner algae is treated, the easier it is to remove.

 

Keep your pool crystal clear all season.  The best way to fight algae is to prevent it before it starts. Regular testing, proper filtration, balanced water chemistry, and routine cleaning will keep your pool looking beautiful and ready for family fun all summer long.  At FillPools.com, we're committed to helping homeowners enjoy clean, healthy pools. Whether you're filling a brand-new pool, topping off after repairs, or preparing for the swimming season, our fast and reliable pool water delivery service helps you get back to what matters most—making memories in the water.

 

Need your pool filled or topped off? Contact FillPools.com today for dependable pool water delivery throughout Pennsylvania and Northern Maryland!