How to Add Algaecide to Your Pool

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Dirty pool (Photo: @YulianaStar via Twenty20)
A swimming pool is just as much work as it is fun. Not to mention, a major expense. Staying on top of routine pool maintenance means keeping the water balanced, the filters clean, and the skimmers free of debris.
It’s easy to fall behind on upkeep but the longer you put it off, the harder—and more expensive—it becomes to restore a neglected pool. Don’t wait until your water is cloudy and the lining is coated with slippery green slime before reaching for the algaecide.
Pool algae is one of the biggest threats to the health of your swimming pool and one that can easily snowball out of control.
There’s not much you can do to prevent algae spores from finding their way into your pool surfaces. Once they’re in, rainstorms, excessively hot weather, and other conditions can exacerbate algae blooms and compromise the structural integrity of your pool.
Consistent use of algaecide can preserve your pool and save you money in the long run.

What is Algaecide and how does it work?

Algaecide is a chemical used in swimming pools to kill algae and prevent future algae from growing.
Shock your pool: The first step in ridding your pool of algae is to dramatically boost its chlorine levels, also known as shocking the water. Pool technicians suggest shocking your water once every two weeks, or after long dormant periods between seasons. Algaecide should be used more frequently after heavy use during the summer months, or if you’ve recently hosted a pool party. Every 3 to 5 days should suffice.
Allow time for chlorine levels to balance: The chemicals in pool shock kits can sometimes react with the chemicals in algaecides. For that reason, you must never add them to your swimming pool at the same time. Wait up to at least 24 hours after shocking your water before adding the algaecide. This gives your pool’s chlorine levels adequate time to level out. Because of the effect that heat and sun can have on the potency of chemical shock kits, it’s best to add them in the evening hours.
You can find pool shock kits and algaecide at any major hardware store or pool supplies store.
Determine the type and amount of algaecide you need: Exactly how much algaecide you need will depend on the size of your pool along with other factors. Follow the algaecide instructions based on your pool specifications. Adding an excess amount can result in skin and eye irritation, so don’t overdo it.
In severe cases, use a pool scrubber brush to go over the lining to remove or loosen excess algae before adding the algaecide.
There are many different types of algae. Some types of algae may not respond to all kinds of algaecides. The most common type of algae is green algae, which is easy to treat with an all-purpose algaecide. Pink algae is not a true algae, as it is caused by bacteria, and responds best to bromine treatment. Mustard algae (or yellow algae) responds best when treated with a copper-based algaecide. Non-metallic algaecides containing polyquaternium WSCP work best against harmful black algae spots that tend to cling to the pool’s lining.
Add algaecide to the pool water: Once you’ve determined the correct amount of algaecide by reading the label directions, pour it into the pool in several places to ensure it can circulate. Switching on the swimming pool pump and letting the pool filter do its job will also help move the algaecide along.
Allow the algaecide to sit overnight: The following day, remove dead algae by vacuuming.
Repeat if needed: Don’t be alarmed to find your pool is still cloudy with algae the day after applying the algaecide. Some types of algae are stubborn and may require multiple doses of algaecide before you achieve your desired results.