Black algae (also known as ‘blackspot algae’) can be the bane of a swimming pool owner’s life – if left to get out of control.

‘Black algae’ is not actually black in colour. Like most algae, it is ‘blue-green’, but it is such a dark blue-green that it appears black. Don’t mistake it for mould though. Black mould is something different altogether. Mould is a fungus. Algae is a plant. It’s a plant that lives in water, both salt and freshwater, but really thrives in warm water with lots of sunlight. Exactly what the algae spores will get from your summer swimming pool. The spores float about looking for opportunities to grow somewhere. You can’t avoid them. So, the trick is how to prevent them taking root and infesting your pool.

Prevent algae from infesting your swimming pool:

Prevention is the best cure. You can prevent black algae from growing by:

  • Maintaining a regular cleaning schedule to scrub the sides of the pool – even if you don’t see anything growing there
  • Ensuring there’s enough chlorine / maintaining the right PH balance
  • Running your pump and filter every day to maintain flow and clean debris
  • Not letting the water turn green – and using pool shock to clear the water quickly if it does.

Once it has taken hold: removing black algae from your pool:

It’s not easy to remove black algae from your pool. It takes hard physical labour to scrub it off the sides of the pool. You will need to:

  • Empty the pool
  • Scrape and brush the algae off with a metal-backed bristle brush
  • Vacuum the pool
  • Possibly repaint or resurface the pool (but ensure the algae is gone first)
  • Ensure that all fixtures, lights, pumps and pool toys are free of algae too.

Once you have refilled the pool, you must adhere to a diligent cleaning and maintenance schedule as per above, to stop the algae coming back.

Keep the chlorine levels high initially, and through the winter months, and cover the pool to keep it free of falling leaves.

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