How, When and Why to Use Algaecide What is Algaecide? When to add algaecide Types of Algaecides What algaecide is best? How much algaecide? Can you swim with algaecide? Recommended Brands

How, When and Why to Use Algaecide

What is Algaecide?

Most pool owners know the joy of swimming in crystal-clear water. Unfortunately, that excitement fades when presented with unsightly algae growth. What does one do when facing a swimming pool full of green slime? While prevention is the best way to fight algae growth, there is a way to combat algae once it has infiltrated your pool.

Enter algaecide, a specially formulated chemical designed to kill swimming pool algae and prevent regrowth. Used in combination with pool shock, algaecide can be a powerful ally in the fight for a clean, clear swimming pool.

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What is algae?

Algae is a living plant that thrives in water and bright sunlight. Not only does algae look gross, it can also clog your pool’s filtration system and pave the way for harmful bacteria to settle in your swimming pool (some types of bacteria love to feed on algae). The most common type of swimming pool algae is green, but you can also find black and yellow algae -- and both of these varieties are tougher to kill than green algae.

When should you add algaecide to your swimming pool?

The best time to add algaecide to your pool is after you’ve scrubbed, vacuumed, and shocked your swimming pool using a shock treatment that’s at least 70% chlorine. Using algaecide after shock treatments is a good way to kill any tiny algae spores that the pool shock missed -- and algaecide can also help prevent it from growing back.

Of course, this isn’t the only time to use algaecide: It’s also smart to add algaecide to your pool water before you close your pool down for the winter and when you open it again in spring or summer. You can also use algaecide to help prevent algae before it grows -- some pool owners like to add a dose of algaecide to their pool water on sunny days (remember, algae loves the sun!), and other pool owners treat their water with algaecide once a week as part of their regular maintenance routine.

Pro tip: For best results, add algaecide to your pool during the day, while the sun is out (this is when algae is most likely to grow). For a comprehensive guide to getting rid of algae, click here.

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What types of algaecides are available?

Quat Pool Algaecides

Quat algaecides, short for “Quaternary Ammonium” compounds disinfect your swimming pool, effectively washing away algae. Because Quat algaecides are detergents, adding too much causes excess foaming, odor and staining. This is the most economical algaecide solution.

Polymer Pool Algaecides

Polymer pool algaecides, or Poly-Quat compounds suffocate algae growth, clearing swimming pools at speeds up to two times faster than Quat algaecides. In addition to its faster speed, another advantage Polyquats have over Quats is that they neither foam nor stain.

Metallic Pool Algaecides

Metallic pool algaecides like silver algaecides are especially effective on black and yellow algae. Metallic algaecides are the most powerful of the three, therefore can be expensive. Most metallic algaecides are made with copper which can cause staining of pool walls and hair.

Sodium Bromide

Technically, sodium bromide is not an algaecide. However, this powerful compound kills and prevents swimming pool algae.

What is the best swimming pool algaecide?

When it comes to selecting an algaecide, your best choice is a formula that’s designed for your specific needs, including:

When it comes to selecting an algaecide, your best choice is a formula that’s designed for your specific needs, including:

Types of Algae

Some algaecides only treat green algae. Others treat black algae or yellow (or “mustard”) algae. And still others are designed to treat all types of algae. Make sure you choose the formula that will treat your problem.

Age of Algae

The older algae becomes, the more difficult it is to control. Treat the problem as soon as it is noticed.

Your Budget

Some algaecides are more expensive than others. For example, a polymer-based algaecide won’t foam or stain your pool surfaces -- but you’ll pay more for this option. Copper-based algaecides, on the other hand, are more affordable but can cause staining.

Severity of Algae Problem

For a less severe, a standard polymer- or metallic-based algaecide will likely do the trick. For a super-stubborn outbreak, you might want to use a sodium bromide-based algaecide instead. Follow the instructions on the algaecide to kill all growth.

Sunlight and Water Temperature

It is best to treat when algae is actively growing. Sunny days and a water temperature of 60°F or higher is helpful

Presence of Bacteria

A red or pink color -- especially around any of your pool’s plastic fittings or pieces of swimming pool equipment -- is an indication of bacteria growth. Look for an algaecide that kills bacteria in addition to algae.

“Pink” algae isn’t algae.

This reddish-pink growth isn’t a true algae. It’s a type of bacteria – in this case, a slimy bacteria that thrives around PVC pipes and in shady spots on your pool’s surface.

How much algaecide should you put in your swimming pool?

The amount of algaecide you should use will depend on the size of your pool (in gallons). Not sure how many gallons your pool uses? Use our Pool Volume Calculator to calculate your pool’s volume. For best results, follow the instructions on the algaecide package.

It’s worth noting that, although it’s not dangerous to use too much algaecide, your pool water will foam if you overdo it. The good news is, the foam isn’t harmful, and it’ll go away on its own.

Can you swim with algaecide in pool?

Yes, you can -- although it’s a good idea to wait 15 to 30 minutes before swimming after you add algaecide to your pool.

Although algaecide isn’t harmful, there’s a chance that it can irritate your skin and eyes if you dive in immediately after you treat your pool. And if you’re using a metallic/copper-based algaecide, the metal content could affect your hair color!

Additional Algae-Removing Products

In addition to your algaecide of choice, some other items you’ll want to keep on hand for the prevention and elimination of algae are:

Recommended Brands

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