Black Algae is very bad news for a pool-owner or a pool-user. Not only is is ugly and VERY difficult to eradicate, it can also cause respiratory problems when spores are inhaled in tiny droplets of pool-water.
WARNING Black algae spores can grow in the the lungs, nice and safe in a warm, chemical-free environment!
Black algae spreads in several ways.
- It grows laterally along the grout lines of a tiled pool or on an cement surface, pool-liner or painted pool.
- It spreads by releasing water-borne spores, which colonise other areas of the pool.
- Water that is splashed out of the pool, will evaporate and the spores can then be trodden or blown to different areas.
- It can (and IS) transported from pool-to-pool on swimming costumes and other items like arm-bands and goggles,etc.
If you detect black algae - also known as blue-black algae - act swiftly to prevent an expensive disaster from occurring
Black algae form a layered structure where the first layer (which Superchlorination may kill) protects under-layers from further destruction
Therefore a pool afflicted with this type of algae needs a lot of work to eradicate it completely
Treatment for a moderate attack of black algae
If there are only one or two patches of black algae it is sometimes possible to eradicate it without draining the pool: -
- Apply Copper Sulphate, at a rate of 3 grams per cubic metre, via the skimmer
- Do not overdose with Copper Sulphate
- Check pH and adjust as required
- Superchlorinate to 10 ppm
- Brush the algae spots with a stainless-steel pool brush to remove all visible signs
- Turn the pump off and use crushed Chlorine tablets, contained in a cloth bag or an old sock, and tied to a length of cord, to spot treat the algae (not recommended for vinyl-liner or painted pools)
- On cement or tiled pools black algae spots can also be rubbed with a Chlorine tablet - wear gloves for doing this
- Pour a good concentrated all purpose algaecide on the algae spots and leave it in contact with the algae overnight
- Turn the pump and filter back on, then brush dead algae from the surfaces
- Brush the black algae each day until it is no longer visible
- In severe cases repeat treatments will often be necessary
- Vacuum the pool, check and adjust pH and then superchlorinate again
- Ensure that Chlorine levels are maintained to prevent further attacks
Treatment for a bad attack of black algae
- The best solution to eradicating black algae is to drain the pool, acid-wash and jet-wash the tiles, then irrigate the entire surface of the pool with liquid chlorine (Sodium Hypochlorite)
- Allow this to remain in contact with the tiles for at least an hour and then jet-wash the pool again
- NOTE! - do not allow hydrochloric acid and sodium hypochlorite to mix or they will produce deadly Chlorine Gas.
- Repeat acid- and jet-washing until every visible trace of Black Algae has been removed.
After the visible black algae has been removed from the pool: -
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Ken Walker - MyPoolGuru©