Algaecide or Shock First

While shocking and adding algaecide is very effective in killing off algae, they should not be done together. This is because when you mix chlorine and algaecide together, it renders both of them useless. There is a sequence of treating a pool with stages of algae. Which chemical do you add first? Algaecide or Shock?

You should first shock/super chlorinate your pool to levels above 5 ppm-scrub the walls & floor of your pool then wait for the chlorine levels to fall below 5 PPM. When they do, add algaecide to your pool. This will kill off the rest of the algae and provide a preventative solution to your pool H2O. 

The secret, my experience, especially in a bigger pool, is to brush the pool floor, steps, and walls with a long handle pool brush and add chemicals in sequence If a green pool develops get right on it before it gets worse because it only will and read this article for complete instructions.


Algaecide or Shock First


Step 1-Shock First

Heavy shocking with granular chlorine will generally require 24-48 hours above 5 ppm before the chlorine demand level has dropped to safe swimming levels (below 5 ppm). Add Algaecide

The right dose of Chlorine kills algae and realistically acts like an algaecide when you add it to the pool water. If the chlorine is balanced, Shock first. Algae should not be a huge problem. Unfortunately, Algae is stubborn and looks for ways and places to grow.

For this reason, using an Algaecide after a huge dose of chlorine can help keep them away, and if your pool succumbs to algae can help clean up the mess much faster. Follow this article that will help you through what all pool owners go through.

Like chlorine, algaecides also kill algae, but they typically work more slowly.

You should start seeing a transformation after 24 hours. If you have green pool water after shock, it is imperative to think about your water and pool safety. Hence, don’t use the pool after 24 hours. First, do another pH test to get clearance, and then backwash your filter a final time, and you are good to go.

*All algaecides work by releasing positive-charged ions into the water, which combine with the negatively charged algae particles. Algaecides don’t break down in sunlight the way chlorine does, so they remain available much longer. Some algaecides are preventative and won’t remove algae once they establish themselves in your pool.

The best way to deal with a green algae-filled swimming pool is to super-chlorinate the pool and then add algaecide to the pool water. It’s going to take some time to do this.

Most algaecides are not intended as a standalone treatment against intense algae problems but are rather intended to be used preventatively or as a follow-up to other treatments like shocking or super-chlorination 


Different Types of Pool Algaecide



Like chlorine, algaecides also kill algae, but they typically work more slowly.

  • Algaecide has a copper base that attacks algae and stunts their growth.
  • There are different types of algaecide: quat pool algaecide, metallic pool algaecide, polymer pool algaecide, and sodium bromide.
  • While algaecide is formulated specifically to get rid of algae in a pool, chlorine is still the most effective solution to killing algae.
  • You should add algaecide to your pool every week as a secondary sanitization option.


Quat Pool Algaecides

A Quat pool algaecide, also known as a Quaternary Ammonium compound, is utilized as a microbial disinfectant. They are positively charged and attach themselves to algae cells that are negative. Once they are bonded with the algae, they disintegrate the exterior protective membrane.

If you want the most bang for your buck, this is an excellent algaecide option that comes in both 50% and 10% concentrations. 

Metallic Pool Algaecides

This type of pool algaecide holds Copper ions, a trusted solution in water treatment for thousands of years. To minimize potential pool staining from overuse, the copper gets attached to amino acids. The positively charged metal ions fix themselves to the algae, invade the algae walls, poison the enzymes, and attack the nucleus of the cell.

Metallic pool algaecides are an ideal option for black algae and are also useful against algae blooms. Most average copper algaecides run between 7% and 9% copper strength or concentration.

Polymer Pool Algaecides

Polymer pool algaecides are Poly-Quat compounds with longer chains of carbon. These are versatile algaecide options because they are both non-staining and non-foaming. These negatively charged polymers spread over the algae cell’s surface much more quickly and surround the cell for the kill.

Poly-Quats are expensive, much longer-lasting, and more effective than regular Quat algaecides but are also costly. These algaecides usually get sold in 60% and 30% strengths or concentrations.

Most copper algaecide products will kill off all algae in your pool within the first 24 hours after you have added it. If you have a very large algae problem, you may experience a longer wait time.

Most algaecides are effective on multiple strains of algae, but certain stubborn strains, such as black spot and mustard algae, benefit from using specialized algaecides. Before shopping for an algaecide, determine the type of algae present in your pool based on the color, texture, and patterns that you observe.



 Pool Algae in Swimming Pool


The first signs of Algae may not look like algae.

Algae is a single-celled plant form. It uses the process of photosynthesis to make its own food. It comes in a very wide variety of colors and forms and is adaptable to almost all conditions. Because of algae’s microscopic size, it takes literally millions of these plants to accumulate to be noticed by the naked eye! By that time, it may be too late and very costly to correct.

The best way to eliminate algae is through prevention!  Don’t let it start, but if it does, then Jump on It!  Algae happen in in-ground pools, above-ground pools, freshwater pools, and saltwater swimming pools.

There are 3 main types of Algae associated with a swimming pool:

  • Green algae- can cling to the wall or float in the water. Get rid of it by brushing the sides and floor of the pool, shocking, and adding Algaecide. The most common type of algae causes you to notice green water in your pool. They are caused by a lack of proper filtration and sanitation, which often leads to an elevated pH level in the pool.
  • Black algae- looks like black spots and feels slimy. Get rid of it by brushing the algae and adding Algaecide- Such algae can appear in your pool if someone, before entering the pool, swam in a natural body of water (ocean, river, lake, etc.) and did not wash their swimsuit after that.
  • Mustard algae- looks like sand on the floor of the pool. Get rid of it by brushing the algae and adding algaeecide. They are more common in southern countries than in northern ones. However, yellow algae (also called mustard) can appear in all pools. If the pH or alkalinity of your pool is abnormal, this may be the cause. Debris, phosphates, and pollen can also cause yellow algae.


First, before using a pool algaecide, analyze and balance the swimming pool water.

  • If the pool is full of algae, add a flocculant (floc) to the water and vacuum up the coagulated algae that settle on the bottom of the pool.

Prior to and during treatment, you should thoroughly brush the algae in order to “break open” the slime layer. This is an important step. If you skip it, you’ll prevent the treatment from working.

Shock the pool very aggressively. As a guide to follow, shock treatments should be used before algaecides start the process. Wait for the residual to come down and brush the algae to loosen.  Add substantial amounts of strong Algaecide. Once the chlorine level rises in your swimming pool water after adding shock chlorine, you will see the swimming pool react Keep pool filters running in fresh or salt water pools.

Add Pool Algaecide After Pool Shock


Step 2-Add Algaecide

You do not need to wait for your pool to go green before you Shock it. In fact, you should Shock your pool every week. In the summer, don’t wait longer than two weeks. But what about Algaecide? Do you add Algaecide Before Or After Shocking your pool? Once the pool is shocked and the residual comes down below 5ppm, go to step 2.

Algaecide should always be added after Shock. Shock is considered complete only when your pool loses less than 1 ppm of chlorine overnight. Add algaecide only after the chlorine level has dropped to 5 ppm or less. High levels of chlorine make the active ingredients of algaecide ineffective. Algaecide should be used after each shock treatment.

A Small amount to a large amount of algaecide should be added after every shock treatment for a quick treatment process. 

The role of algaecide to kill algae is secondary. The primary role of algaecide is to prevent the growth of algae growth in the next 5 – 7 days after shock. To be effective in this role, the algaecide should be well dissipated throughout the pool. Algaecides usually require a shock treatment before application anyway, so just be sure to shock the pool first.

It is very important to run the pool filter & pump while adding Algaecide. It is best to start the filter pump just before adding Algaecide and let it run for 2-4 hours to ensure adequate circulation. If white foam develops on the surface of the pool, it will dissipate after a while with the filter on.

Your pool water pump should be left running for about 24 hours following the addition of an algaecide in order to get the products adequately circulated, so be sure to override your pump’s timer if you have one set up.

* Depending on the number of algae that is killed, You may have to use a Flocculant chemical that adds weight to the suspended solid, which will help settle these solids to the pool bottom to be vacuumed out of the pool.

Or use a Clarifier chemical, sometimes called a Pool Water Polisher, for fewer amounts of solids suspended in pool water that will make solids bigger so that they are trapped in the filtering system. 

How Long Does it Take for Algaecide to Work


Algaecide acts in the pool for five to seven days. Watch your pool for several days, and run the pump regularly to see if the mold comes back. After five-seven days, you can add algaecide in low concentrations as a preventative for algae control. Shock can complete the algae removal process.

During the hot summer months, adding a copper-based algaecide can be a preventative while keeping your home pool open. If you add too much algaecide, foam appears, but note that it will dissipate over time.

The pool algaecide will slowly fade due to chlorine, so you can shock the pool with higher chlorine levels to speed up the process and wait a few days after shocking. Even if you do not do this after you add algaecide, the cloudiness, which is pool algae, will disappear in about a week or two at the most.

Although the algaecides that are used for most pools are low in concentration so that you can swim right away, it is advisable to wait a few minutes to an hour. Let the product spread throughout the pool, especially if it has copper in its composition, since you don’t want to have colored hair, right?


Adding Algaecide to Swimming Pool


If you use an Algeacide step by step correctly, as well as calculate the correct dose for your pool and not overdo it, algaecides you can consider it a safe product for your health. You can even swim with it, but remember that it is always better to wait for a little while before immediately swimming.

Adding algaeacide in a swimming pool to kill or prevent algae from growing in your swimming pool would be the best way to offset any type of algae. Using a chemical calculator for Algaecide, pool shock, or pH chemicals is the best function of preventative maintenance.

Its job is to interrupt important processes inside the algae, stopping photosynthesis or provoking an explosion of the algal cell walls. It is best to use an algaecide in combination with a chlorine sanitizer to keep the pool water clean.

Most algaecides are copper-based, which are chemical compounds with metal as the central atom. Such a chemical disrupts the normal cellular processes inside the algae, thus killing them and preventing them from developing.


  1. Make sure all of the filtering systems of your pool, including the pool pump, are working properly.
  2. Before adding algaecide, the chlorine level in the pool should normally be between 1 and 3 ppm, parts per million.
  3. Super-Chlorinate the pool water and let it stand for 24 hours until it returns to a safe level.
  4. Add the correct amount of algaecide to the pool following the instructions on the package. For the best results, use the online algaecide calculator.
  5. Leave your pool to sit after adding algaecide for 12 or more hours or overnight and vacuum all dead algae in the morning.
  6. Adjust your pool pH and keep a close eye on chlorination levels.  If the concentration is above 6 ppm, the pool is still unsafe to swim in.
  7. Add algae concentrate or copper chelate solution to the water, depending on the needs of your pool.
  8. Mix it in a bucket with pool water and broadcast, covering the circumference of the pool surface.

Using Algaecides for Algae Control


Algae like to grow in stagnant water, so you need to make sure your swimming pool’s water is always circulating throughout the pool. Clogged or poor running pumps will create an optimum environment for algae to get comfortable.

At least twice a week, you should check and clean your skimmers and pump strainers. The secret, especially in a bigger pool, is to brush the pool floor, steps, and walls with a long handle pool brush. If you balance your pool water and keep it balanced.

Use preventative copper-based algaecides as a maintenance step. You could be in better shape this pool season during those “dog days of summer”    

How Long After Adding Algaecide Can You Shock?

While shocking and adding algaecide is effective in getting rid of algae, it should not be done together. When you mix chlorine and algaecide, it renders both of them useless. You should first shock the pool and wait for the chlorine level to become normal (1-3 ppm), after 24 hrs or so, and then add an algaecide.………………………………….. Read more


JimGalloway Author/Editor


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