How to Get Rid of Pool Algae

Are you having a huge party, and now your pool water is green? Or, are you the kind of person who constantly has green pool water no matter what you do? Does it seem like there is no way to get rid of the algae in your pool?

Well you are in luck, because we are going to explain how to get rid of pool algae.

Pool Algae: 3 Ways to Get Rid of it

First, let’s learn a little bit about algae and how it’s formed. According to the Merriam-Webster dictionary it’s:

…a plant or plantlike organism of any of several phyla, divisions, or classes of chiefly aquatic usually chlorophyll-containing nonvascular organisms of polyphyletic origin that usually include the green, yellow-green, brown, and red algae in the eukaryotes and especially formerly the cyanobacteria in the prokaryote.

To simplify, algae is small plant-like organism which grows in pool water. There are three common forms:

  • Green or blue algae
  • Yellow or mustard algae
  • Black algae

1. Green Pool Algae

This is the most common of all swimming pool algae because it grows due to lack of proper sanitation and filtration.

Sometimes you see this algae free-floating in your swimming pool which can cause your entire pool to turn green.

This algae may also cling to the wall of your pool or at the bottom. It’s really easy to brush off and become free floating.

The good thing about this type of algae is that it’s easy to get rid of. It may only show up in  little spots in your pool that have poor circulation. A little sanitizer or algaecide does the trick to fix it.

2. Yellow Pool Algae or Mustard Algae

Mustard algae grows on the walls of your swimming pool in spots that don’t get a lot of sun. It’s the second most common algae you find in swimming pools. Sometimes it can be mistaken for sand or pollen that can collect in your pool.

This algae is difficult to get rid of and won’t be killed off by any normal dose of sanitizer (such as chlorine) or an algaecide. You need to kill it by super shocking your swimming pool and adding a product along with chlorine like Optimizer or Chelated Algaecide, or else you’ll battle it all season long.

3. Black Algae

If you ever had yellow algae and thought that was tough, think again. Black algae is awful, although, it’s not very common. What makes this algae so hard to get rid of is the defense mechanism it processes and it’s strong roots.

This algae looks like little dark black spots on your swimming pool wall.

The part that you can see has a protective layer on it to protect itself. The roots are strong and grow deep into the plaster of your pool walls.

Just like yellow algae, this strain can appear even if you are taking care of your pool normally, and all your sanitation levels are correct. To kill it you need a strong pool brush and lots of shock.

Why Do I Have Green Pool Water?

Where there’s water, there’s algae. This is why swimming pools need to be treated with chemicals. This ensures nasty bacteria and other growths don’t get into your water.

The main reason algae grows in your pool is because it hasn’t be treated with a sanitizing chemical, like chlorine, or it hasn’t been treated enough. When your pool is lacking sanitation, and the water is stagnate, you’re going to get algae.

That’s why it’s important to keep the pool water moving with your filter and pump. It’s hard for algae to grow when the water is moving.

Algae also loves dark places that don’t get much water circulation including:

  • under your ladder
  • on your pool steps
  • corners, creases and crevices
  • inside the pool filter – algae likes to grow here especially when your pool isn’t circulating

These are all great spots for algae to feed and multiply.

So now that you have a general understanding of what pool algae is and why it forms, you must destroy it!

Method #1: Get Rid of Pool Algae by Superchlorination (Shock)

There are three different stages of algae. You need different amounts of shock for each:

  • Light green algae
  • Dark green algae
  • Black green algae

These are not different types of algae; it’s just different amounts. Thus, the more algae in your pool water, the darker the green color.

Light Green Pool Water

If you have a light green pool, you need to double shock your pool in order to kill algae. One pound of shock treats up to 10,000 gallons of water. So, if you have a 10,000 gallon pool or less you need to double shock it by adding two pounds of shock.

If you have a 20,000 gallon pool or less, you need to add four pound bags of shock. And if you have 30,000 gallons or less you need to add six6 pound bags and so on.

Dark Green Pool Water

If you have a dark green pool you need to triple shock it. So, if you have a 10,000 gallon pool or less, you need to add three pound bags of shock.

If you have a 20,000 gallon pool or less, you need to add six pound bags of shock. If you have 30,000 gallons or less, you need to add nine pound bags and so on.

Black Green Pool Water

Quadruple shock is called for when your pool looks like some sort of creature from outer space.

So, if you have a 10,000 gallon pool or less, you will need to add four pound bags of shock.

If you have a 20,000 gallon pool or less, you need to add eight pound bags of shock, If you have 30,000 gallons or less, you need to add 12 pound bags and so on.

Note: If you have a vinyl liner pool, you should dissolve each 1 lb. bag in its own bucket of water before putting it in the pool. This prevents your liner from being bleached out by the shock. In addition, NEVER POUR SHOCK THROUGH THE SKIMMER IF YOU HAVE AN AUTOMATIC CHLORINATOR. Calcium Hypochlorite which is found in shock, mixed with trichlor, which is found in most chlorine tablets, creates a deadly explosive green gas. And remember, always shock at night. Chlorine burns off 1 PPM (Part Per Million) every hour in direct sunlight causing the chlorine to drop below break-point oxidation required to kill algae.

Method #2: Floc Your Swimming Pool

Floc (or Flocculant) is a chemical that takes all small particles in your pool (like algae) and settles them to the bottom. After all the particles have settled to the bottom, it’s your job to vacuum them OUT of your swimming pool.

This method is more work and can be time consuming, but it gets rid of algae fast – if done correctly.

Here is a step by step guide on floccing your swimming pool:

  1. If you have a multi-port valve on your filter, shut off your pump and turn the valve to “Recirculate” or “Recycle.” This stops the water from flowing through your filter. All this does is spin the water around to help mix the chemical in.
  2. Add the recommended dosage of Flocculant to your pool. Floc comes in liquid and powder form. Make sure you check the directions for the right dosage for your size swimming pool.
  3. Circulate the water for about two hours to get the chemical fully mixed in. Then shut off your pump and let it sit overnight. During this time, the chemical starts to bind the particles together and settle them to the bottom of the pool. In the morning, you should wake up to a nice healthy particle cloud at the bottom of your pool.
  4. Hook up your manual vacuum cleaner. Before you turn your filter on, make sure you have your multi-port valve set to “Waste.” When you vacuum this thick cloud OUT of your pool, you don’t want that thick water going through your filter. Your filter is not powerful enough to clear the water that fast, so cloudy (or green) water will just shoot back into your pool through the return lines. You don’t want this. Finally, make sure you hook up your backwash hose to the backwash/waste port and direct the hose where you want your dirty water to go.
  5. Add your garden hose to the pool and turn it on while you vacuum. Since you are vacuuming to “waste” which dumps a lot of water out of your pool, it’s best to have your garden hose replacing the water with clean water as you vacuum out the dirty stuff.
  6. SLOWLY vacuum the bottom of the pool. You are sucking out thick, dirty water from your pool, and as you move the vacuum across the pool floor, it’s going to kick up debris. When it becomes too cloudy to see what you’re doing, shut off your pump and let it sit for a couple of hours to resettle. Then you can go back and continue vacuuming. You may have to to do this several times depending on how much debris you need to vacuum (this is hard work).

If you’re willing to work this hard, you can have your pool cleared in one day.

Finally, when you are done vacuuming the pool and everything looks good, double shock your pool to make sure ALL the algae has either been removed or destroyed.

Method #3: Use Swimming Pool Algaecide

Normally algaecide, like pesticide, is only a preventive. You want to use it throughout the pool season. But there are some algaecides that contain b14 or metals, such as copper or silver, which can kill algae. These algaecides may have to be added in large doses, but when they work with shock, they can do the trick just as effectively as plain shock. (Note: Never directly mix algaecide and shock.)

Algaecide is best used as a preventive. You can add a few ounces every week to prevent algae from growing in your swimming pool.

To sum it up, some algaecides DO kill algae. Make sure you consult your pool company to find out which algaecide to use.

Which Method Is The Best?

All of these methods work. Method 1 kills all the algae, and Method 2 might be necessary if you need the algae out quickly.

Your best bet is to consult your pool dealer who can assist you with the best method for removing and preventing algae growth in your pool!

Source: Swim University