How to Get Rid of Blackspot Algae in a Swimming Pool

Unsightly black algae can ruin the appearance of any swimming pool. Black algae are a stubborn type of algae that appear as dark black or blue-green spots or spores. The algae grow roots and form a protective layer around itself. It is difficult to get rid of black spot algae but with persistence, muscle power and the right chemicals you can obtain results.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Chlorine tablets
• Algaecide
• Stiff brush
• Gloves

1. Know the chemistry of the pool water by using a testing kit. Black algae form in pools because of low levels of chlorine. You need to test for the levels of pH, alkalinity, chlorine and other elements.

2. Balance the pool water to the correct levels by adding the necessary chemicals. Recommended level figures for chlorine, pH and other elements depend on the size and type of pool (see Resources). Step 1 and Step 2 can prevent algae formation but if there is already the presence of algae formation then continue to Step 3.

3. Shut off the pool pump and then use chlorine tablets to spot treat the black algae spots.

4. Pour algaecide on the spots. Leave the combination chlorine and algaecide treatment on the algae overnight. Using algaecides can effectively kill and prevent algae.

5. Scrub the algae spots the following day. Wearing gloves, use a stiff brush to scrub the spots and then vacuum. Repeat the process if there are any remaining spots.

6. Check your filter system to ensure it is clean and then start the filter pump for circulation. Be sure to adjust the valving for optimum circulation. Retest the pool water for pH and chlorine levels and adjust levels if necessary.

7. Implement a program of chlorination and the use of an algaecide to prevent a reoccurrence of this problem in your swimming pool.

Tips & Warnings

• Monitoring the pool water, adding algaecides and ensuring proper filtration and circulation can prevent the formation of algae.
• When there is the presence of black algae spots, just shocking/chlorinating and or adding algaecide may not work. You need to aggressively brush the affected area and repeat the process until the algae is gone.
• This procedure cannot be used on vinyl lined pools.

Resources

• Get information here on pool size.
• See here for information on recommended chemical levels.