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 be blown back into the pool and start spreading again.  We have removed black spot from dozens of pools that have already been acid-washed just a few months earlier!

Remember, 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, with our treatments, the problem can be fixed 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.

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 sold cheap because they add coloured water to the product to reduce the price. This dilution means that there are less powerful active ingredients that are needed 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 means that the life source is removed right away.  It also causes algae to become vulnerable to their 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

Signs of Black Spot algae:

  • Raised black spots on the pool surface
  • Spreading and multiplying over time
  • black lumps in corners and steps
  • Shock chlorination only helps slightly
  • Spots feel slimy to touch
Algae in pool
Black spot algae
black spot algae in walls
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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 believed to be the main cause behind algae growth as they form part of the ‘food’ that algae need to survive.  Most pool experts agree that if phosphates are removed from 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 just need to be kept low with your water balanced and chlorinated properly.

Factors that encourage Black Spot

  • Foliage near pool with Black Spot
  • Constantly low chlorine levels
  • Constantly high pH
  • Lack of Shock Chlorination
  • Very high phosphates
  • Very old ‘rough’ pool interiors

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.

Leaf stains 7
Algae stains
Algae stains
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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 pools surfaces because the surface is 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 black spots may look exactly like black spot algae, most times it is not an algae but mineral and metal deposits in the form 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 can be usually be removed with our stain treatment products.  So don’t be fooled, 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 spots in fibreglass swimming pool
black spot algae in pool

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 metal staining.  Our customer mistakenly believed that the metal 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.

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

OPTION 1 – Black Spot Stain Removal DIY kit

What We Do 1


black spot algae


Algae stains 7



  • Simple step-by-step instructions included
  • Phone support from our technicians
  • Pool does NOT need to be drained
  • Kit is tracked and delivered by Fastway Couriers
  • Kids are back in the pool in just 7 days
  • Kit is $295 for pools 40,000+ Litres
  • Long-life algae prevention included


Enquire now!

OPTION 2 – Black Spot Stain Removal – On Site Technician


black spot algae


Algae stains 7



  • 2 Litres of imported (2 step) high concentrate algaecide killing formula
  • High strength granular chlorine to shock the pool and catalyse the algaecides
  • Pool does NOT need to be drained to treat algae
  • Kids are back in the pool in 7 days
  • Visit is $465 for pools 40,000+ Litres


Enquire now!

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.

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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 steps. Furthermore, low chlorine levels, warm temperatures and very high phosphates are the perfect combinations for algae growth.  We can 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 somewhat 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 in 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 cement and cause permanent damage and discolouration to your pool interior. Also, the black spot also forms a protective surface layer that makes it resistant to chlorine.  Our quality process and products will remove black spot within a few weeks.

Remember, some pool shops mistakenly believe that black spot can NEVER be removed and even 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.  REMEMBER: YOU DO NOT NEED TO DRAIN YOUR POOL TO REMOVE BLACK SPOT.  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.