How to Remove Algae from Pool Walls and Floor

Algae in your pool? You’re not alone. It’s one of the most common—and frustrating—issues pool owners face. A little green on the wall can turn into a full-blown swamp if not handled quickly. Whether it’s green, yellow (mustard), or the dreaded black algae, removing it from your pool walls and floor requires a strategic approach.

The good news? With the right steps and some elbow grease, you can banish algae and reclaim your crystal-clear water. Let’s break down exactly how to tackle algae buildup, prevent it from returning, and keep your pool walls and floor looking like new.

1. Identify the Type of Algae

Not all algae are created equal. Knowing what you’re dealing with helps you choose the most effective treatment.

  • Green Algae: The most common type—floats in water and clings to walls. Slimy, green patches.

  • Yellow Algae (Mustard): Sticks to shady areas and pool walls. Harder to remove and more chlorine-resistant.

  • Black Algae: Looks like dark spots or blotches. Has deep roots and penetrates surfaces—very stubborn.

Each type needs a slightly different cleaning intensity. For black or yellow algae, be prepared for repeat treatments.

2. Test and Balance the Pool Water

Before diving into cleanup, balance your pool water to maximize the effectiveness of your treatment.

  • pH Level: Aim for 7.2–7.4 to help shock work better

  • Chlorine Level: Should be at the higher end of the safe range

  • Alkalinity: Keep between 80–120 ppm

  • Calcium Hardness: Check if necessary, especially for plaster pools

Use a reliable test kit or take a water sample to your local pool store.

3. Brush the Pool Walls and Floor Thoroughly

This is a MUST. Brushing loosens algae from surfaces so chemicals can do their job.

  • Use a stiff-bristled brush for concrete or plaster pools

  • Use a nylon brush for vinyl or fiberglass pools

  • Focus on corners, steps, and shaded areas—algae loves hiding there

  • Brush twice daily during treatment for best results

Don’t skip this step—it’s key to breaking the algae’s stronghold on your pool walls.

4. Shock the Pool (Heavily)

Algae hates chlorine—but you’ll need a strong dose to knock it out.

  • Use 3–5 times the normal amount of shock treatment, depending on the severity

  • For black algae, use a calcium hypochlorite shock

  • Run the filter continuously for 24–48 hours after shocking

  • Avoid swimming until chlorine levels return to normal

Always shock at dusk or night so sunlight doesn’t burn off the chlorine too quickly.

5. Apply an Algaecide for Extra Power

While shock kills most algae, algaecide helps eliminate stragglers and prevent regrowth.

  • Use a polyquat or copper-based algaecide depending on algae type

  • Follow product directions carefully—do not overdose

  • Circulate water for several hours after applying

Algaecide is especially useful against yellow and black algae, which tend to be chlorine-resistant.

6. Vacuum and Backwash the Pool

Now that algae is dead, it’s time to get it out of the pool.

  • Vacuum manually (don’t use the automatic cleaner) to waste, if possible

  • Remove all dead algae from the floor and steps

  • Backwash your filter after vacuuming to remove trapped algae and prevent recontamination

If your filter is really dirty, consider deep cleaning or replacing the media (sand, cartridges, etc.).

7. Run the Filter System Continuously

Filtration is your best friend during cleanup.

  • Run the pump for at least 24–72 hours straight

  • Monitor pressure gauge and backwash when needed

  • Add a clarifier if the water remains cloudy

Proper circulation helps eliminate residual algae spores and polishes the water.

8. Prevent Algae from Returning

Once your pool is clear, prevent future outbreaks with consistent maintenance.

  • Keep chlorine levels steady (1–3 ppm for standard pools)

  • Brush and vacuum weekly, especially in corners

  • Shock after heavy pool use or rainstorms

  • Test water 2–3 times per week

  • Use a weekly algaecide if you live in a warm, humid area

Prevention takes less time than battling a full algae bloom!

Conclusion

Removing algae from your pool walls and floor might feel overwhelming, but it’s entirely doable with the right plan. Identify the algae, brush vigorously, shock heavily, and don’t forget filtration and follow-up care. With this process, you’ll not only eliminate the current infestation but also fortify your pool against future breakouts.

💦 Ready for a pool that’s clean, clear, and algae-free? Get scrubbing, keep testing, and stay ahead with regular maintenance!

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