The Ultimate Guide to Getting Rid of Pool Algae (All Types)

Algae is a nasty pest that can take over a pool almost overnight. Getting rid of it is a pain, but it's a battle you can absolutely win. We'll show you exactly what to do to kill the gunk and keep it from returning.

Identifying Different Pool Algae Types for Better Treatment

Knowing what type of algae your pool has helps you choose the right plan to get rid of it. Each one looks and acts a little differently, so a quick ID is the best first step.

Green Algae

This is the most familiar type. It floats in the water, turning it anywhere from a light haze to a dark green swamp. It also coats the walls and floor, making them feel slimy to the touch. Green algae usually show up when your chlorine levels are too low, your filter isn't running long enough, or the pool gets too much sun. High phosphate levels in the water can also feed it.

Yellow Algae (Mustard Algae)

This stuff looks like a yellowish-brown dust or pollen that settles on the pool floor and walls, especially in shady spots. You can brush it away easily, but it often returns to the same spot a few hours later. It's more resistant to chlorine than green algae and can be very persistent.

Black Algae

Black algae are the toughest to defeat. It appears as small, hard black spots that feel rough and are very difficult to scrub off. The real problem is that it grows deep roots into the pool's plaster, making it extremely hard to kill completely. You have to scrub these spots aggressively to break through their protective layer, usually introduced from outside sources, like contaminated swimwear or equipment.

Pink Algae (Pink Slime)

This one is a bit of an impostor—it's actually a type of bacteria, not algae. It forms a slimy, pinkish-red film that you'll often find on plastic surfaces like skimmer baskets, ladders, and pool toys. It thrives in areas with low water circulation and can be a sign that your pool accessories need a good cleaning.

Pool Algae Removal Tools & Chemicals You'll Need

To get rid of all the above-mentioned algae for good, you need the right gear. Having this stuff ready before you start makes the whole process much easier.

Essential Tools

• Pool Brushes: Have both a nylon brush for general cleaning and a stiff-bristled (or stainless steel, if suitable for your surface) brush for tougher algae like yellow or black.
• Vacuum: A manual vacuum that can send water to "waste" is crucial for heavy algae outbreaks. For routine cleaning and preventing debris buildup that can feed algae, an automated solution like the iGarden Pool Cleaner K60 can be a huge help, efficiently vacuuming your pool floor and walls.
• Skimmer Net: For daily debris removal.
• Water Test Kit/Strips: A must-have for regular water chemistry checks.

Key Chemicals

• Shock Chlorine: Granular (calcium hypochlorite or dichlor) or liquid (sodium hypochlorite) chlorine.
• pH Adjusters: pH Increaser (soda ash) and pH Decreaser (dry acid).
• Alkalinity Adjuster: Sodium bicarbonate (baking soda).
• Calcium Hardness Adjuster: Calcium chloride.
• Phosphate Remover: If your phosphate levels are high.
• Specific Algaecides: For different algae types (green, yellow, black).
• Clarifier: Helps gather tiny particles, making them easier for the filter to remove after the algae are dead.

General Steps for Clearing Pool Algae Effectively

Once you've identified your algae type and got all the tools ready, you can begin the general pool algae removal process. Getting rid of algae is a four-step process: you physically remove as much as you can, balance the water, kill the rest with chemicals, and then filter out the mess. Follow these steps, and you'll get your pool back.

Preparation is Key

Before you start pouring in chemicals, a little prep work will make the job much easier. First, test your pool water for pH, chlorine, alkalinity, and phosphate levels, and write down the numbers. Then, use a net to scoop out any large debris like leaves and twigs, and be sure to empty your skimmer and pump baskets so nothing gets clogged later.

Physical Removal of Algae

With the big stuff gone, it's time to attack the algae itself. The first step is to brush every surface of your pool—the walls, the floor, the steps, and any little corners. You need to scrub hard to break the algae loose. For slimy green or pink algae, a standard nylon brush will do, but for tough yellow or black algae, you'll need a stiff, steel-bristled brush to break through its protective shell.

Immediately after brushing, vacuum the pool. It is very important to set your filter to the "waste" setting. This sends all the dirty water and dead algae you just brushed off directly out of the pool, instead of running it through your filter, where it could just get stuck or be sent back into the water. Move the vacuum head slowly and carefully to capture as much of the gunk as possible.

Chemical Treatment: Shocking the Pool for Algae

Shocking pool for algae is the main chemical attack. Check your pH one last time and adjust it if needed, since chlorine works best in balanced water. It's best to shock in the evening, as the sun burns off chlorine quickly. For a standard green algae problem, you might use two or three pounds of shock for every 10,000 gallons of water. For stubborn yellow or black algae, you'll need to hit it hard with a double or even triple dose. Dissolve the shock in a bucket of water first, then pour it around the edge of the pool. For stubborn or widespread algae, you might need to shock the pool multiple nights in a row until the water starts to clear and you can maintain a high chlorine level.

Filtration: Cleaning Up the Remains

After the shock has done its work, your final job is to filter out the aftermath. Keep your pump running 24/7 until the water is completely clear. All that dead algae will clog your filter fast, so you will need to clean it frequently. Be prepared to backwash your sand or DE filter, or rinse your cartridge filter, multiple times until the cloudiness is gone.

Specific Treatments for Different Algae Types

While the basic steps work for most algae, you may need a special approach to get rid of them for good, especially for those four types of algae.

Green Algae Treatment Focus

For green algae, a heavy dose of shock is usually enough to kill them. The key is to be aggressive. Bring your chlorine level up high and keep it there for a day or two. If green algae are a constant problem for you, check your phosphate levels. Phosphates are algae food, and using a phosphate remover can help starve out any future blooms.

Yellow Algae Treatment Focus

Yellow algae, also called mustard algae, are more stubborn. You will need to be extra thorough with brushing, as it can resettle on surfaces very quickly after being disturbed. After shocking the pool, follow up with an algaecide specifically made to kill yellow algae. These products are designed to break through its defenses.

Black Algae Treatment Focus

Black algae is the hardest to defeat because it grows deep roots into your pool's surface. You must scrub the black spots with a wire brush to break open their tough, protective outer layer. For very stubborn spots on a plaster pool, you can carefully place a chlorine tablet directly on them for a few minutes to kill the roots. Be very careful not to let it sit too long, as it can damage your pool surface. Copper-based algaecides are also very effective, but be sure to follow the directions to avoid staining your pool.

Pink Algae Treatment Focus

Pink slime is actually a bacterium, not an algae, so it requires a different plan. You will need to use a chemical specifically designed to kill bacteria. Because it spreads so easily, you must also pull out and scrub all pool toys, ladders, and floats with a strong cleaner. This bacterium can hide in your filter system, so a deep cleaning of your filter is also necessary. Consider a filter cleaner specifically for this purpose, and run a powerful backwash or chemical flush through your lines.

Algae Prevention Strategies for a Clear Pool

Keeping your pool clear is much easier than cleaning up a green mess. A simple, steady routine will stop algae from ever getting started.

• Test Your Water Weekly: Always know your numbers. Make sure your pH, alkalinity, and chlorine levels are where they should be.
• Maintain Chlorine Levels: Your chlorine should always stay between 1 and 3 ppm. This is your number one defense against algae.
• Run Your Pump Daily: Let your pump run for at least 8 hours every day to keep the water moving and clean.
• Brush and Skim Regularly: Brush the pool walls and floor each week, and keep your skimmer baskets clear of leaves and other debris.
• Shock the Pool Periodically: A light shock every week or two, especially in hot weather, kills any stray algae spores before they can grow.
• Use a Preventative Algaecide: For extra protection, add a small maintenance dose of algaecide each week, especially if your pool is prone to algae.
• Remove Algae Food: Phosphates feed algae. Quickly skim out any leaves or grass clippings, and be careful with lawn fertilizer near the pool.

When to Call a Pool Professional for Algae Help

You can handle most algae problems on your own, but sometimes you need to call for backup. Don't hesitate to contact a pool service if you're facing these tough situations.

• The algae keep coming back. If you've tried everything and the green stuff returns, a pro can find hidden problems with your equipment or water that you might miss.
• You can't get the water chemistry right. If you keep adding chemicals but your test kit numbers are still way off, it's time for an expert to step in.
• Your filter might be broken. If the filter is making strange noises or the pressure is always high even after cleaning, a professional can diagnose and fix it.
• You're not comfortable handling strong chemicals. Dealing with large amounts of shock or algaecide can be tricky. A pro can do the job safely and correctly.
• The water won't clear up. If you've killed the algae but the pool is still a cloudy mess, a professional can figure out why and get it sparkling.

FAQs about Pool Algae

Q1: My pool water is still cloudy after removing algae. Why?

Cloudy water after algae removal usually means there's a lot of dead algae still suspended in the water, or your filter needs more cleaning. Keep your pump running and clean your filter regularly. Using a clarifier can also help gather these small particles for easier filtration.

Q2: Can I just use algaecide without shocking the pool?

Not really. For a real algae problem, algaecide alone isn't strong enough. Shocking the pool is what actually kills the algae. Think of algaecide as a helper you use after shocking, or as a weekly treatment to prevent algae from growing in the first place.

Q3: How long should my filter run when clearing algae?

You should run your pump 24/7 without stopping until the water is completely clear. Depending on how bad the algae were, this can take a few days. Remember to clean your filter daily, because all that dead algae will clog it very quickly.

Q4: Can algaecides harm my pool liner or equipment?

Most algaecides are safe for your pool surfaces if you follow the directions. The main one to be careful with is copper-based algaecide. Using too much of it can leave stains, especially on plaster or light-colored linings. Always read the label.

Q5: Does my pool need algae prevention in winter?

Yes. Algae can still grow in cold water, just much more slowly. If you close your pool for the season, be sure to add a winterizing algaecide. If you keep your pool open year-round, just continue with your normal chemical and cleaning routine.