Black Spot in pool

Black spot algae

Don’t drain and acid wash your pool to remove black spot algae because it will just come back again.  Draining the pool is not effective because the algae also lives in the pipework, solar heaters, filter and pump.  This means that once the pool is acid-washed and refilled, the algae living in your pool equipment will blow back into the pool and start spreading all over again.  We have removed black spot from dozens of pools that have already been acid-washed just a few months earlier!

Before After Swimming Pool Chlorinegreen algae after
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Copper Stains in Swimming Pools The Pool Stain Removers 1

Algae is one of the most frequent issues pool owners face.

However, of all the different algae types, black spot algae are the hardest to remove.  Thankfully, our treatments fix the problem easily and quickly without draining the pool water. Our long-lasting treatments also help prevent it from coming back.

Finally, our products will completely wipe out many forms of algae and bacteria that normal chlorine levels cannot. In most cases, our quality algaecides will clear your green pool water within 48 hours and completely remove the black spot, green algae and mustard algae within a few weeks. In short, this treatment kills, mustard algae, green algae, pink slime and black spot algae.

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Certified technicians with 10 years experience.
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Signs of Black Spot algae

Black Spot algae

Factors that encourage Black Spot

How to remove black spot algae

The best way to remove black spot algae is to use quality algaecides that use a two-step process to isolate and kill the black spot algae.  Remember, all cheap one-step algaecides are heavily diluted with water to give the customer a feeling of value for money (eg. two litres feels like better value than one).  These algaecides are cheap because they add coloured water to the product to reduce the price. This dilution simply means less active ingredients to do the hard work.  Our algaecides have no added water, food colouring or fillers added to reduce algae killing strength.  What you are buying is pure active ingredients, not fillers, food colouring and water.

On the other hand, we use a proven two-step process when removing black spot algae.  Firstly, the Part A algaecide stops the black spot from being able to absorb oxygen.  This removes the life source of the algae right away.  It also causes the algae to become more vulnerable to its surroundings.  Secondly, the Part B  algaecide gets into and kills the black spot algae from the top to the roots at the bottom.  This two-step process kills black spot algae completely without draining the pool or acid washing.  We have done this more than 4,000 times over the years with amazing results. Remember, without this two-step process, the algae will just come back!

We strongly suggest that you act on black spot algae as soon as possible. Remember, if black spot stains are left for longer than 2-3 years, the algae roots can sometimes penetrate the pool interior and discolour your pool surface permanently.

Types of black spot algae

black spot algae
Copper stain reacting with chlorine
black algae
Algae stains
black spot algae
black spot algae in pool
black spot algae

What causes black spot algae in pools?

There are two main factors that lead to algae growth – high phosphate levels and/or poor chlorination.  Phosphates are the main cause behind algae growth as they form part of the ‘food’ that algae need to survive.  Most pool experts agree that without phosphates in the water, algae will struggle to survive.

On the other hand, it is not true to say that algae will grow if there are low phosphate levels present in the water.  For example, properly balanced and filtered water will not allow algae growth, even if low levels of phosphates are present in the water. Therefore, it is not necessary to constantly add expensive products to remove small amounts of phosphates. Remember, phosphate levels must be low and your water balanced and chlorinated properly to keep algae away.

Kill black spot without draining the water

Most black spot, mustard algae, yellow algae and green algae can be completely removed using our treatments on any pool finish including Pebblecrete, Quartzon, fibreglass, glass bead or fully tiled pools.  As the images show, we have removed Black Spot algae and other algae stains from swimming pool surfaces without draining the pool water.  Best of all, we can keep it gone.

If you are unsure of the type of stain you have please feel free to speak with us.

Before After copper stains on pebble poolcopper stains on pebble pool

Black spot in fibreglass swimming pools

It is very uncommon for black spot algae to form in a fibreglass pool.  This is because black spot algae cannot attach to fibreglass pool surfaces because the surface is too smooth and difficult to penetrate.  For this reason, black spot is not able to get properly embedded in your pool as it does in pebble pools.  Although some black spots may look exactly like black spot algae, most times it is not algae but mineral and metal deposits in the form and shape of black dots.  The picture shows what black spot algae in a fibreglass pool can look like.

Black spots in fibreglass pools are either osmosis or mineral deposits from pool salts or algaecides.  These spots will usually disappear within a few days with our stain treatment.  Remember, it is very likely that an algaecide designed to kill black spots will do absolutely nothing at all to remove the spots.  This is because the spots are not algae. In fact, treating these spots with an algaecide will make them worse!


Black spot in swimming pool? Are you sure?

Please call us if you are unsure of the type of staining you have as the wrong treatment can make it much worse.  This image is of a pool that initially had mild copper staining.  Our customer mistakenly believed that the green copper stains were black spot algae.  He then treated it with granular chlorine to remove the stains and within an hour most of the pool surface turned black.  This happens because granular chlorine will oxidize the copper sulphate and turn it black in the presence of granular chlorine.  

Remember, treating a metal stain with high strength chlorine and algaecides will oxidize the metal staining and make it even darker!

Black Spot Stain Removal

Most Popular

OPTION 1 Black Spot Stain Removal DIY kit

$ 245

OPTION 2 Black Spot Stain Removal – On Site Technician

$ 415

Removing copper from pool water

CuLator Metal Eliminator removes copper and most other metals from pool water. This helps to prevent metal stains from appearing in your pool later on. Algaecides may contain a copper sulphate complex that should be removed a month after treatment. CuLator Metal Eliminator is unique because it can physically remove copper and other metals from pool water. Your pool shop will help you to measure the copper levels in your pool water. We have more information about CuLator Metal Eliminator here.

Culator Metal Eliminator

4 Types of algae found in swimming pools

Green algae are the most common and fastest-growing algae types found in swimming pools.  It will often turn your pool water green or cloudy overnight!   It most commonly starts in corners or areas where automatic pool cleaners are unable to access, such as corners or steps. Furthermore, low chlorine levels, warm water temperatures, and very high phosphate levels are the perfect combination for algae growth.  We remove green algae in less than 48 hours and keep it gone.

Mustard Algae is usually easy to brush off the walls and floor of your pool, but it will often quickly return. It grows in shady areas of the pool which are protected from sunlight or areas of poor circulation. So just like black spot, yellow algae is also resistant to normal chlorine levels.  Our treatment will remove mustard algae in less than 72 hours.  If you think you have mustard algae but it does not react to brushing, you may have iron staining.

Black spot algae is unique because it grows on the walls or floor of your pool.  It often starts in areas with low circulation and will not brush away like other algae. It also spreads slowly and is often mistaken for mould because it forms dark spots on your pool surface.  So we suggest that you act on this type of algae quickly as its roots (algal spores) can penetrate into the pool pebbles and cause permanent damage and discolouration to your pool interior. Also, the black spot also forms a protective surface layer (biofilm)  that makes it resistant to chlorine.  Our quality process and products will remove black spot algae within a few weeks.

Remember, some pool shops mistakenly believe that black spot will NEVER go away and usually suggest acid washing as a remedy.  However, when the pool is drained, the algae is still alive in the filters and pipework.  This means that once the pool is refilled the algae quickly returns.  We have removed black spot without draining more than 2,500 times.  


 If you have a fibreglass pool please contact us for more information.

Unlike other forms of algae, pink slime is actually a bacteria, not algae.  It often appears around skimmer boxes, lights, ladders and other areas of the pool. If not treated promptly, it will continue to slowly spread around the walls and floor of your pool.  We are able to remove pink slime algae for you.   However, it is not very common in Australia.