How to Remove Algae From a Salt Water Pool
- Matt Giovanisci
A salt water pool is not much different from a regular chlorine based swimming pool. Salt in your pool water runs through an electrically charged line after it has been filtered and is turned into chlorine. So, you still have a chlorine pool, but the way you add chlorine and kill algae is slightly different.
You might think that by having a salt water pool, you shouldn’t add chlorine. This is NOT the case.
Most salt water systems come with a button or switch that will allow you to “super chlorinate” the water. This is not a replacement for chlorine shock. Super chlorination will not be strong enough to oxidize your pool. With this said, you should still shock your pool weekly.
Super chlorination should be done monthly, but it will not help you get rid of algae. In order to remove algae in your pool, you are going to have to use conventional shock.
How to Shock a Salt Water Pool
First, get your water tested. You can test it yourself with test strips, or take a sample to your nearest pool supply store. Make sure you pH and alkalinity levels are correct. You want your pH to be 7.4 to 7.6 and the alkalinity to be between 120 to 150 ppm (parts per million).
Hint: Having your pool water properly balanced will the shock to be more efficient.
Then, you need to determine the color of the pool from the algae. If you salt water pool is light green or teal, then you should double shock your pool using standard calcium hypochlorite shock.
Before shocking, it’s best to take a pool brush and brush the walls and floors of your pool. Algae likes to cling, if you break it up the chlorine shock will have a better chance of killing it. Be sure to pay particular attention to creases, crevices, behind ladders, and pool steps.
One pound or bag of shock treats up to 10,000 gallons of water. So if your pool is 10,000 gallons or less, you would add two pounds of shock to your water. Remember to add shock only at night to allow the shock to be more effective. Also, keep your pool running for at least 8 hours to allow the shock to circulate throughout the water and kill the algae.
If you pool is green or dark green you should triple shock your pool. Again, if your pool is 10,000 gallons or less, use three pounds of shock.
If your pool is black from algae (and this may only happen in the beginning of the year of if you neglected your pool for weeks or months), then you will have to quadruple shock it using 4 pounds per 10,000 gallons of water.
After Shocking, Your Pool Should Be Cloudy Blue
After your pool has been shocked, you should wake up the next morning to a cloudy blue pool. This is exactly what we want. The cloudy water is usually caused by the dead algae, which turns a light grey when it’s killed. At this point, your filter should do the rest.
Keep your filter running 24 hours a day until the pool is clear. You can also add a water clarifier to help speed up this process. It’s also safe to swim in the pool if it’s cloudy. The movement in the water will help the filter get rid of the dead algae particles.
[Get more information on clearing up a cloudy swimming pool]
What If My Pool Is Still Green?
If your pool is still green or teal, you will need to repeat the shocking process. I would recommend buying enough shock to do this twice in case this happens. You should shock the very next night. After that, your pool should be cloudy blue and you can proceed with clearing it up.
If your pool is still not cloudy blue after shocking twice, there may be other issues with your water chemistry. Here are some things to troubleshoot this issue:
- Make sure your pool water is properly balance.
- Visit a local pool store to get your water tested before shocking.
- Have them check for chlorine lock or chlorine demand if they can.
- Shock only at night or dusk.
- Keep your filter running during the shock treatment.
How To Prevent Algae from Growing
Keeping your pool properly balanced and sanitized is the key to keeping all forms of algae from growing. Make sure you
- Keep your pH, alkalinity and sanitizer levels in the correct range at all times.
- Run your pump and filter for 8 to 12 hours a day all season long.
- Keep your pool clean by regularly vacuuming and brushing.
- Shock your pool every week. 1 pound per 10,000 gallons.
- Keep your additional pool equipment clean including pool toys, floats, ladders, steps, diving boards, slides, solar blankets and covers.