The Battle Against Algae

Anytime we are faced with an invader, the best way to keep it from settling in and taking over, is to stop the invasion before it happens or at least as soon as it is discovered. Algae are those kinds of invaders and no one wants their pool ruled by these annoying, single-celled plants.

Like any kind of plant, algae thrive in the perfect environment:

Continued from Tips page – warm temperatures, sunlight, moisture, which is rarely missing in a swimming pool, and a cozy spot for them to put down roots.

This plant is not unfamiliar to most pool owners. They have fought this enemy for years.  Once you discover algae digging in for a fight in your swimming pool, it’s time to bring out all the weapons you have available to you. However, just throwing those weapons at the enemy won’t necessarily win the battle. It’s imperative that you fight smart.

• First of all, it’s important to know your enemy and their invasion tactics. All of the following can be introduced to your pool through organic debris brought into the pool via rain and wind storms.

• The most common invader is green algae. It can cling to the walls, but can also float in the water. Luckily for us, it’s also the easiest to defeat

• A tougher opponent is yellow algae, AKA mustard algae. You guessed it; these are yellow with shades of green and brown and sometimes looks like dirt or sand at the bottom of the pool.

• Then there are the dreaded black algae which are usually a dark blue-green that appear to be black. It will often present as coin size spots on the pool walls.

One of the most important ways to prevent an invasion is to make the battle ground, or water in this case, inhospitable to the algae in the first place. This is where the ppm and other abbreviations come in. Yes, we all took chemistry in school and many of us forgot it as soon as we finished our final exam. Fortunately this stuff is easier to remember.

Algae cannot survive in an environment which is well sanitized. For our swimming pools this means chlorine levels at 1.0 to 3.0 parts per million, or PPM. But Chlorine alone cannot win the war against the evil algae. Proper pH must be maintained as well. Chlorine needs a good environment to do its job and that is water with a pH of about 7.2 to 7.6. Water below this range, in other words acidic, will require added sodium carbonate, or soda ash to bring the pH up. If your reading is higher than 7.6, it’s time to add some muriatic acid which lowers the alkalinity. These are the numbers you want to maintain under normal circumstances. However, if you see you are already under attack you will need to call in backup. You will also need to bump up your pH to around 7.8 to 8.0.

• You will need to brush the walls, paying close attention to any surface where algae growth is visible. When green algae is the issue, a nylon brush will work well. If you are dealing with yellow or black algae you will need to use a metal brush, although a metal brush should not be used on tile or vinyl pool surfaces. Since yellow and black algae imbed themselves in the porous or cracked surfaces of a plaster pool, and tiled pools and those lined with vinyl don’t have such an environment, a nylon brush should work on these surfaces. Brushing will open the pores of the algae so that the chemicals can penetrate the cells.

• Now circulate, circulate, and circulate some more. While treating for algae, be sure to backwash your filter and keep the circulation running 24 hours per day until the algae problem subsides. While we are on the subject of circulation, make sure the return jets in your pool are positioned for optimum water circulation. It is especially important to be sure that areas where algae have formed are receiving the circulation benefits of the return jets.

• At this point it’s time to shock the water. No, not by swimming naked. Shocking is adding large quantities of chlorine to quickly and thoroughly sanitize the water. Be sure to follow the manufacturer’s directions. If needed, shock can be repeated up to three times over a 36 to 48 hour period.

• Once chlorine levels have dropped to 5.5 ppm it’s time to add algaecide. Once the algaecide is added be sure to brush the pool again to loosen any algae still clinging to pool surfaces. You will then need to thoroughly vacuum the pool. If you find that algae are floating on the surface of the water, there are products available which will bind all the algae together allowing them to fall to the bottom of the pool for easier vacuuming.

• Once your pool is free of algae, you will need to keep it debris free too. Therefore it is important to keep your pool skimmed and empty your skimmer baskets at least once a week.

A very important note to keep in mind is that if your pool surface is cracked or decaying, you may be fighting a losing battle. The algae live in the porous and cave like areas found in aging pools and algaecide and brushes just can’t penetrate these areas. You may see some temporary benefit, but the problem will continue to return until their fortress is destroyed. Yep, I’m talking about resurfacing, but that’s a whole other article.

If you would like more information about algae control or even resurfacing your pool, contact AquaSense Pools. We can advise you on what is your best course of action.

Safe swimming,
Your team at AquaSense Pools

THEPool Group, McKinney, TX


Phone: 214-799-7739


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We have received FANTASTIC service from Travis. We have used many other companies in the past for weekly cleaning that have not done a good job or been reliable. Travis is very reliable, honest and professional. He does a great job taking care of our pool. I would highly recommend this company!!! Travis goes above and beyond!!! Best pool service we have ever had!!!!

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Provided weekly pool services. Very helpful for the first time pool owner. Helped us understand the maintenance needs of the pool and how to operate. Easy to communicate with. And responds quickly. Additionally, they helped with some pool equipment upgrades and were very mindful of cost.

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Best pool service we have ever had. Our chemicals are always in balance, no more problems with summer algae bloom and the quick and caring response to our questions are very appreciated. Travis has provided first-rate service consistently.

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