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How to Get Rid of Pool Algae

Causes of Algae

Improper pool water chemistry can lead to algae formation. Algae forms more easily with warmer weather. Low chlorine levels, high pH and insufficient pool water circulation all contribute to algae formation. During warm weather it’s very important to keep the pool water circulating through the pump during the day. Still pool water in sunlight is perfect for algae development. In Las Vegas with our warm weather we recommend setting the pump to circulate 1 hr for every 10 degrees F. So for 90 degree weather, the pump should be set to run for 9 hrs during the daytime. If you pool water is heated try to keep it no warmer than 84 degrees. Free chlorine levels which are too low or too high (over 5ppm) is dangerous.



Green Algae

Green algae is the easiest to treat because it is sensitive to chlorine. If a little green algae is present and the bottom of the pool can be seen, the algae can easily be treated. First test the pool water for Total Dissolved Solids. If the pool is a salt free pool and the TDS is over 2500 ppm (or 5500 ppm for a salt pool) you’ll want to go ahead and drain and refill with fresh water. If TDS levels are okay, then test the alkalinity and pH.

Normal alkalinity is between 80-120, with 100 being optional. Fill water in Las Vegas is on the alkaline side. The higher the number, the more alkaline the water is. If the alkalinity is too high, follow instructions with the test kit to lower alkalinity with muratic acid. Add acid to the pool will the pump circulating. After acid is added, wait a little while – perhaps 30 minutes to recheck alkalinity which should now be in the normal range.

Normal pH is between 7.2 and 7.8 with 7.4 – 7.6 being ideal. The higher the pH, the less effective chlorine is. Follow instructions on the test kit to add the correct amount of muratic acid to lower pH as necessary. In Las Vegas, fill waters pH is 8.0 so it’s more likely pH is too high. Acid is added to the pool with the pump on. After acid is added wait approximately 30 minutes and verify pH is in the normal range.

Now with both alkalinity and pH in the normal range, add enough chlorine to shock the water. It’s important to get the chlorine high enough to kill the green algae and to have enough free chlorine left over to sanitize the pool. Again, add the chlorine with the pump on. The green algae should start disappearing immediately. The pool water may appear cloudy or a little aqua green.

Make sure the filters are clean so they’re able to clear the water. Set the pump times to run 1 hr for each 10 degrees F of high daily temperature. 90 degree days = 9 hrs a day.

If you need Blue Water Pool Service to clean your pool filters, call 702-243-7946.

Test the cyanuric acid to be sure there’s enough stabilizer to hold chlorine in the water, about 30-50ppm. In a few days, check the chlorine levels to make sure there’s enough chlorine to prevent a green algae from forming again (1-3ppm). Never swim in water above 5ppm total chlorine. If the water doesn’t become sparkling clean within a few days there may be a damaged filter, filter manifold, or some other problem. Call Blue Water Pool Service at 702-243-7946.

If the green algae is so severe that the pool looks like a swamp and it’s hard to see the bottom of the pool, it’s better to have the pool drained by Blue Water Pool Service. The pool and filters may need an acid wash or chlorine bath while it’s empty.

Anti-entrapment drain covers probably need to be installed. Plaster can be severely damaged when left to dry out, so your pool will be refilled immediately after the cleanup. Startup chemicals will then be added.

Yellow Algae

Yellow algae looks like mustard on the pool walls and is a little more difficult to eradicate. Yellow algae has a coating which makes it harder for chlorine to get inside the organism and kill it. There are commercial algaecides like “Yellow Out” or “Silvertrine”, which have detailed instructions on how to fight this algae. Even a well kept pool can be susceptible to yellow algae. It’s best to prevent the algae in the first place. Purchase a preventative algaecide and start using it regularly as directed when the weather starts to get warm in the spring time. As with green algae, the same guidelines still apply for circulation, chemistry levels, brushing the pool walls, and cleaning the filters. See the sections on green algae.

Black Algae

Black algae is rare and, oftentimes, misidentified. It appears as small black spots on the tile line around the pool. It has a waxy shell on it and is difficult to get rid of. True black algae is treated with very strong chlorine applied directly to the spots. Chlorine pucks (tri-chlor) that are used in chlorine floaters can be used to scrub the algae. Use a pool brush with metal bristles to brush the black algae. Then with a gloved hand, scrub the algae. Be very careful not to scratch pool tile with the metal brush.