How to Clean Black Algae

If a pool has not been properly maintained or has become contaminated, black algae can take root. They must be treated as soon as possible. Black algae grow deep into the substrate and armor themselves with tough, waxy protective caps that resist penetration by regular cleaners. Removal requires diligence and persistence.

1. Test your pool and adjust water chemistry to optimum levels.
2. Inspect pumps and circulation patterns. The presence of black algae indicates poor circulation. Adjust circulatory patterns so all water in the pool circulates evenly.
3. Sanitize your filter.
4. Sanitize a stiff-bristled brush. Use stainless steel if possible.
5. Brush the black spots vigorously 3–4 times a day for as many days as necessary. Be extra diligent around corners, ladders, and fixtures. Scoop and vacuum any debris and sanitize all tools after each use.
6. Wear personal protective equipment like gloves and eyewear before handling any chemicals. Review Safety Data Sheets. Black algae have protective caps and roots, so frequent scrubbing is needed to allow the chemicals to reach them.
7. Scrub a chlorine tablet directly on each black algae spot while wearing protective equipment.
8. Shock your pool according to the manufacturer's instructions for black algae treatment. A dose 3x the normal strength may be recommended. Consult a pool supply professional.
9. Allow the pool to stabilize and re-test the water.
10. Apply a copper-based algaecide under the following conditions:
    • Alkalinity is between 50–160 ppm
    • pH is below 7.6
    • Copper levels will remain below 1 ppm
    • Water temperature is above 15°C (60°F)
    • No biguanide-based sanitizing system is present
    The algaecide must contact the algae to be effective. Always follow the manufacturer’s instructions.
11. Clean the filter again.
12. Continue brushing the pool 3–4 times daily for 3 days.
13. Test the pool again.
14. Re-shock the pool if algae reappear. Follow with a second dose of algaecide, clean out debris, and sanitize tools and filters.
15. Continue brushing the pool 3–4 times a day through the second treatment.
16. Repeat if necessary.
17. Maintain proper pool chemistry and brush the walls/floor 1–2 times a week. Once black algae take root, they often return if maintenance lapses.
18. If algae persist, drain the pool. Scrub vigorously and vacuum debris.
19. After refilling the pool, maintain chemistry, ensure proper circulation, and routinely add copper-based algaecide per pool guidelines.

Limited Warranty Notice:

This information is based on E.W. Industries Ltd.’s present knowledge and experience. E.W. Industries Ltd. assumes no liability for such information and advice. E.W. INDUSTRIES LTD. WILL NOT BE RESPONSIBLE FOR CONSEQUENTIAL, INDIRECT, OR INCIDENTAL DAMAGES (INCLUDING LOSS OF PROFITS) OF ANY KIND. E.W. Industries Ltd. reserves the right to make any changes as required.

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