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Black Spot

04 April 2012 swimart

Black Spot

Black Spot

Avoid the dreaded black spot this summer


Has the warmer weather drawn you out into the backyard to prepare for summer, only to find some nasty looking black spots in your pool? If so, it sounds like a case of 'black spot' algae infestation.

Black spot is a particularly difficult algae to get rid of that typically takes up residence on the walls and floors of your pool. It can be considered similar to the black algae that grows on bathroom shower tiles, silicone seams near the bath, or the sides of the fish tank.

Here are some ways you can prevent black spot from invading your pool this summer, plus some treatment options if it has already taken hold over the winter months.

What is it and what causes it?

"Black spot often looks dark green or blue, and tends to grow in the harder to reach spots in your pool," says Chris Fitzmaurice, Swimart Australasian manager. "It can sometimes be mistaken as moss."

The name black spot is given to this particular kind of algae because of the dark spot on top of the growth, which is usually the only visible part; if you only remove this spot, the algae will grow back within a few days. This head protects the layers underneath from destruction.

Black spot is a slower growing algae than most others, but don't let this fool you, as it is very tough to get rid of once established. The algal spores often take up residence on your pool walls and floor when it is empty and grow once it has been refilled with water. Algae growth is caused by an imbalance in the pH of the pool from wind and rain, so maintaining regular chemical treatments will help keep black spot at bay.

How do I prevent it?

Black spot can be hard to remove once it has attached itself to the walls of your pool or embedded in grout between tiles as it is chlorine resistant, so prevention is better than cure.

Keeping your pool's free chlorine levels above 1.5 parts per million can help prevent the growth of black spot and other algae. After putting chlorine in your pool, make sure the chlorine is evenly distributed by keeping the water circulating properly. This is to ensure the chlorine reaches areas where black spot is most likely to grow, such as tight corners and the deeper end of the pool. Regular vacuuming and the removal of leaves will help prevent black spot also.

"It is a lot easier to maintain your pool's chlorine levels so algae such as black spot does not get a foothold," says Chris. "However if it does appear, there are ways that you can remove it yourself."

Disinfectant for your pool is also available to aid in the prevention of black spot, but only apply this to the walls and floors of your pool when it is completely drained.

How do I treat it?

"If you suspect you may have black spot forming in your pool, collect a water sample and bring it into your local Swimart store," says Chris. "That way we can correctly identify what is affecting your pool and direct you towards the most effective treatment."

If you don't have time to bring in a water sample, book a Water Health Check with one of Swimart's technicians and they will come to you. Obtaining the correct chemical treatment for black spot algae is crucial, as other kinds of algaecide may not be as effective as those made especially for this type of growth.

Ask a member of your local Swimart staff or carefully follow the instructions on the algae treatment to ensure all algae is removed properly. For particularly bad growths, repeat treatment may be necessary. If you don't have time or don't want to treat it yourself, book in a Home Pool Health Check and one of Swimart's technicians will treat your pool for you.

Your options

If these prevention tips haven't reached you in time to stop black spot from claiming your pool, never fear. Swimart has everything you need to thoroughly remove your algae problem.

Check these out at your local store:

  • Non-foaming, non-metallic Black Spot Treatment
  • Black Algatrol
  • Black Spot Granular Algaecide (for pebblecrete, white plaster and tiled pools)
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