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Why should I use an algaecide? [open]
While chlorine can treat algae, the most common types of algae are chlorine resistant. Before adding algaecide make sure to have proper pH and alkalinity levels. Algaecides are also great when used as a preventative measure, recommended to be used on a weekly basis to keep algae at bay. [Shop Algaecide]
When should I use an algaecide? [open]
Algaecide should be used when you have cloudy or green water and can be used to treat pool foam.

Algaecide can be used to prevent algae from blooming in your pool. It is also smart to use it after each shock treatment as chlorine can lessen the effects of algaecides, check out our Rx Clear® 3 month kit for a combination of algaecide and super shock. Algaecide is most effective in warm weather but you may also want to use an algaecide as you close your pool for the season. [Shop Algaecide]
What type of algaecide should I pick? [open]
The type you use depends on what you have going on. You should use:

Quat Algaecides if you want to save money and plan to chlorinate your pool at the same time.

Polymer Algaecides if you want to avoid any chance of foaming and staining, want something stronger and faster than quat algaecides, and don’t mind paying more.

Sodium Bromide Algaecides if you have black algae or any other color and aren’t as worried about staining.

Sulfate Pentahydrate Algaecides if you plan to use chlorine with your algaecide and your pool’s algae is out of control.

Once you determine the type of algaecide, you should also take into account the color of the algae and the concentration of the algaecide. [Shop Algaecide]
How do I use algaecide? [open]
Start by checking that your pool’s pH is properly balanced and adjust as necessary. Next, you’ll superchlorinate your water and let it sit until your chlorine levels return to normal. With your chlorine levels back to normal, you’ll add the algaecide according to the package’s instructions. Algaecide works to prevent algae from creating new cells, while keeping the algae is suspension and coating the walls.

The algaecide will need to sit overnight with the pump running, then you’ll vacuum the dead algae the next day. Once your water is clear, consider cleaning your filter. [Shop Algaecide]
Is it safe to swim after adding algaecide? [open]
It is safe to swim in your pool an hour after adding algaecide, but this may limit its effectiveness. For best practice, let it take effect several hours before swimming. [Shop Algaecide]
How does algaecide work? [open]
In basic terms, algaecide works by killing and preventing algae. To get more technical, it stops basic cell processes, though it hasn’t been pinned down exactly how or what processes algaecide stops. [Shop Algaecide]


No matter how much attention you give your pool, sometimes algae forms anyway, leaving you with green or cloudy water. To fight and prevent algae, you’ll want to use an algaecide.

Deciding that you need an algaecide isn’t the same as knowing what algaecide you need. There are multiple different types of algae and multiple different types and brands of algaecide to combat them.
Types of Algae [open]
There are 4 main types of algae common in swimming pools: green algae, yellow or mustard algae, black algae and pink algae or slime.

Green Algae is the most common and is often caused by improper chemical balances or filtration issues.

Yellow or Mustard Algae is rare but persistent and difficult to get rid of. It’s more common in the South.

Black Algae is the most difficult to get rid of. It is most likely to be transferred from a lake, ocean or river.

Pink Algae or Slime is actually bacteria but looks like algae because of its slimy appearance. [Shop Algaecide]
Types of Algaecides [open]
Most algaecides are effective at killing the common types of algae. While you should confirm it will be effective on the algae in your pool, you’ll want to check the active ingredients. The main active ingredients are poly ethylene, sodium bromide and copper sulfate pentahydrate.

Some types also come in different concentrations. The higher the concentration, the stronger it is. The more severe your algae problem, the higher concentration you’ll want. [Shop Algaecide]
Picking a Type of Algaecide [open]
You’ll want to consider a few factors: the color of the algae, how much algaecide is present and the chemical balance of your water.

Some algaecides are designed to be more effective on a certain type of algae while others are effective on all common types of algae.

Additionally, you’ll need to consider the presence of metals in your pool. Some algaecides are powered by copper, which can negatively impact other aspects of your pool. This can lead to oxidization, and discoloration may occur. If you have had issues with metals and minerals in your pool before, you’ll want to avoid this type of algaecide. [Shop Algaecide]
More Questions?
If you’re still unsure about algaecides or have more questions, visit our blog, How to Clean a Green Swimming Pool, or call our in-house pool experts at 1-800-356-3025.