Aquatics: Clean Up the Swamp

Handling Algae in your Pool

The last thing any aquatic facility wants is to have an outbreak of algae. Well-maintained pools should be free from algae. However, there are some things that can turn a maintained pool into a green menace right at the height of swim season. Here are just some of the causes of algae outbreaks.



Rainstorms are notorious for bringing nitrogen into the atmosphere, which can naturally make its way into the pool and convert into nitrates, a food source for algae. Also, when nitrogen in the air comes in contact with raindrops, it is converted to nitric acid which will be carried into the pool. Flooding can cause mud and debris that carries algae into the pool. And, if the power is knocked out and the pump cannot work to circulate water, then things can get bad fast—especially during the hot days of summer.

Pool Parties

Summer is the time for pool parties, so recreational pool water is working overtime. With more people in the pool and the increase in the time they spend there comes higher chlorine demand. Chlorine can be completely consumed within hours during a hot afternoon. This can lead to fast algae growth when the pool is packed with swimmers who bring dirt, bacteria, sunscreen and other organics into the water. Also, if swimmers bring their own life jackets, inflatables or even swimsuits that have previously been in a lake or river, then algae can be carried directly to the pool. If the pool is not super-chlorinated, cleaned and thoroughly brushed soon after the pool party or high-traffic time, then algae can appear rapidly.


Most fertilizers contain nitrogen and phosphorous, two main nutrients for plant growth, and algae is a plant. Spring and even summer can be the time that we are planting and renewing landscapes. The fertilizers used for lawns and flower gardens can make their way into the pool through overwatering or even via the wind. Once the hot weather hits and chlorine demand increases, then algae have plenty of nutrients to get a strong foothold.

Lack of Filtration & Circulation

Water that is moving is healthy water; water that is still will increase the potential of algae. It is imperative that during the hot summer months the pool receives sufficient filter turnover time and good circulation throughout the pool. During the summer, the pool should filter a minimum of six to eight hours per day. Return jets should be positioned to prevent dead spots and to ensure the greatest amount of flow and movement throughout the pool. Many aquatic facilities become concerned about expenses increasing due to energy usage. However, during the summer months, any insufficient filtration can lead to additional cost from increased chemicals and treatments of algaecides. Filtration and circulation are vital during and after heavy swimmer loads.

What to Do When the Pool Becomes a Swamp


Chlorine is still one of the most effective killers of algae, so doing a super-chlorination of 10 to 20 ppm of chlorine can go a long way toward wiping out the algae. Bromine has been shown to be an even faster killer than chlorine, so choose a two-part bromine algae system where you add the algae product and follow with a chlorine or a chlorine-free oxidizer to produce active bromine. These systems can kill algae within 24 hours. Immediately after adding chlorine or bromine algae products, it is important to follow with a chitosan-based clarifier to help floc and remove dead algae to the filter. The clarifier should be dosed at three to four times the normal maintenance and can continue to be used throughout the clean-up process. The pool filter should be run 24 hours until all algae has cleared. Once the algae are cleared, the filter should be thoroughly cleaned. A good preventive algaecide may be added to prevent additional outbreaks through the end of the season.

You may have seen commercials showing oil companies harvesting algae. And what are they harvesting it for? Oil. Algae exudes a hydro-carbon and can leave plenty of oily residue behind in pool water and in the filter media. Using a good broad-spectrum enzyme after a heavy algae growth can help clean the water and surfaces. Also, the enzyme will help break down any additional non-living organic material, which could cause chemicals to degrade faster. Then proceed to your in-season maintenance program, which includes:

  • Shock with chlorine or use a sodium bromide algae product along with chlorine.
  • Follow immediately with a three-to-four-times dose of chitosan-based clarifier.
  • Run filter 24 hours and ensure good circulation and filtration ongoing.
  • Thoroughly clean filter.
  • Test and treat for phosphates if necessary.
  • Add a good preventive algaecide.
  • Use a broad-spectrum concentrated enzyme to clean up oil and non-living organic debris.

Now, the pool is ready for your customers to finish out the season with good quality water.



Terry Arko has more than 30 years of experience in the pool and spa/hot tub industry, working in service, repair, retail sales, chemical manufacturing, customer service, sales, and product development. A certified pool operator (CPO) and CPO instructor through the National Swimming Pool Foundation (NSPF), Arko is currently a water specialist for NC Brands, parent company of SeaKlear and Natural Chemistry, which is a manufacturer of pool and spa products. For more information, visit