Black Spot in pool
Black spot algae
Don’t drain or acid wash to fix black spot algae because it will come back.
Black spot doesn’t just live on the pool surface, it’s hiding everywhere! It’s throughout your system including pipework, heaters, lights, filters, pumps. If you drain and acid wash, the algae hiding in the plumbing blows straight back in, regrowing worse than before.
We’ve treated thousands of pools with severe black spot infestations (see pics below). Many of them were acid-washed just months earlier, only to watch it return. Our three-step, professional-grade treatment process destroys black spot at its source, so it doesn’t come back. Years of research, product testing and failed experiments went into getting this right, so you don’t have to waste time and money on algaecides that don’t work.
How our black algae treatments work
Black spots in pools is no joke. Killing it off takes three steps and if you skip any one of them, it’s just a waste of time and money.
BIOFILM DESTROYER – Black spot is protected by a biofilm layer that shields it from chlorine and most algaecides. Skip this step, and the black spot can resist almost anything. Our first step algaecide dissolves this biofilm, exposing the algae to treatment.
DEEP ROOT ALGAECIDE – With the biofilm gone, our second step algaecide penetrates the algae’s roots to kill it completely. It is also a long-term preventative treatment so it destroys new black spot spores before they can take root and grow.
CATALYST CHLORINE SHOCK – Our high-strength chlorine works alongside the algaecides while they do their job, helping the water fight the black spot directly and pushing both treatments to perform at their highest level.
Des your pool have Black Spot algae?
Here are the most common indicators of black algae in pool surfaces.
- Raised black spots on the pool surface
- Spots spreading and multiplying over time
- Round black lumps in corners and steps
- Shock chlorination only helps slightly
- Spots feel slimy to touch
- Green cloud follows pool brush when scrubbed
If you are unsure about the stains in your pool, please feel free to contact us.
Why does Black Spot Algae grow in pools?
If you want black spot algae to grow like crazy in your pool, do the following.
- Have foliage & leaves in the pool constantly
- Have consistently low chlorine levels
- Allow the pH to drift to very high ranges
- Not shock chlorinating the pool often enough
- Have very high phosphates
- Have an old ‘rough’ pool interior
- Let the pool go green during winter
Black spot algae in swimming pools
If left untreated, black spot algae can damage or discolour your pool surface. The roots burrow deep into porous surfaces like pebblecrete, Glass Beads, and tile grout, where they can contaminate these surfaces over time.
These roots are part of the reason why black spot algae is so notoriously difficult to remove. Scrubbing, or even draining and acid washing, only removes the surface growth. Because the roots survive inside the pool surface, pipework, and filter, the algae regrows, often worse than before.
Our powerful treatment reaches and kills those roots. It also works on other resistant algae and bacteria, including green algae, yellow algae, and mustard algae.
5 reasons why black spot algae keeps coming back
Ever wonder why black spot algae keeps coming back? Here’s the reasons why.
THE BIOFILM WAS NEVER FULLY BROKEN DOWN – Black spot protects itself with a tough shield called biofilm that blocks chlorine and most algaecides from reaching it. If you don’t dissolve this layer away first, you’re only attacking the surface so the algae underneath survives and simply regrows.
THE ROOTS WERE NEVER KILLED – Scrubbing or shocking can knock back what you can see, but black spot’s roots burrow deep into porous surfaces like Pebblecrete, Quartzon, or grout lines. If the roots survive, new spots will resurface within weeks, often right where the old ones were.
DRAINING AND ACID WASHING LEFT ALGAE IN THE PIPES – Black spot also lives in pipework, filters, pumps, heaters, and lights. Acid washing only treats the surface. Once the pool is refilled, algae hiding in the equipment blows straight back in and grows back.
THE RETAIL ALGAECIDE WAS TOO WEAK TO DO THE JOB – Most cheap, off-the-shelf algaecides are heavily watered down and simply don’t carry enough active ingredient to penetrate biofilm and roots. They may stop growth temporarily, but they were never strong enough to kill it permanently.
POOR WATER MAINTAINANCE – Even after a successful treatment, black spot can return if the water is left to turn green and not maintained. Low chlorine levels, high pH, high phosphates, or poor circulation all can work together to encourage the black spots to come back later.
Black Spot Algae Options
OPTION 1 Black Spot Algae Removal - DIY kit
- 1 Litre of Step 1 + 1 Litre of Step 2 Algaecides
- 2 kgs of long-life granular chlorine
- Simple step-by-step instructions
- Phone support from us - even after you buy
- Pool is NOT drained or acid washed
- Kit is sent and tracked by Aramex Couriers
- Kids are back in the pool in 7 days
- Help make water safe for swimming
Most Pools $245
OPTION 2 Black Spot Algae – On Site Technician
- 1 Litre of Step 1 + 1 Litre of Step 2 Algaecide
- Powerful granular chlorine to catalyse the algaecides
- Pool does NOT need to be drained or acid washed.
- Kids are back in the pool in 7 days
- Ensures a safe pool for swimming.
- Visit is $465 for pools 40,000+ Litres
- Note: The kit is simple to do so a tech is often not needed
From $415
Black Spot Remover Price List
| Water Volume | Kit Prices - Inc. GST & Delivery | What You Get |
|---|---|---|
| Up to 40,000 Litres | $245 | 1 Granular Chlorine + 1 Bottle of Step 1 + 1 Bottle of Step 2 algaecide. |
| Up to 65,000 Litres | $295 | 1 Granular Chlorine + 1 Bottle of Step 1 + 2 Bottles of Step 2 algaecide. |
| Up to 95,000 Litres | $345 | 1 Granular Chlorine + X 1 Bottle of Step 1 + 3 Bottles of Step 2 algaecide. |
| Up to 120,000 Litres | $395 | 2 Granular Chlorine + 2 Bottles of Step 1 + 3 Bottles of Step 2 algaecide. |
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5 things that help stop black spot algae
These things will make it very hard for black spot in pool surfaces to come back.
- Remove Phosphates – These are as essential “food” for algae growth. Without these, algae will struggle to grow.
- Free Chlorine – Ensure that you have at least 2-3 ppm of free chlorine in our pool at all times.
- Brush the pool monthly – Giving the walls and floor a good brush will help dislodge and disturb algae that may be trying to take hold in your pool.
- Circulation ‘Dead-Zones’ – Point your return jets to create circular flow pattern throughout the pool, directing water toward dead corners and steps. Run your pump for long enough each day to filter all the water.
- Trim Foliage – Easier said than done, but if you can trim back plants and trees so that the leaf load in the pool is reduced, it really helps.
Black spot algae in fibreglass pools
It’s rare for black spot algae to form in a fibreglass pool because the smooth surface makes it difficult for algae to attach. What looks like black spot algae is often mineral, rust or metal deposits. In some cases, it can be a sign of osmosis, where the surrounding surface becomes raised.
An algaecide won’t remove these spots, since they are not alive or an algae. If you have these spots, our stain treatment kit typically clears them within a few days.
Not sure what you’re dealing with and want to check first? Contact us before you buy. We are happy to help you.
Frequently Asked Questions
The frequently asked questions below are some of the most common questions we are asked about black spot algae. Please feel free to call us if you would like further information.
Do I have to drain my pool water to kill off black spot algae?
No. All of our treatments work with the water still in the pool. There is no draining, even after all the Black Spot Algae is gone.
Won't granular chlorine kill it?
Most of our clients have already tried this before calling us. Over time, black algae becomes more resistant to chlorine so repeated chlorine doses will soon do almost nothing.
Scrubbing and chlorine will damage the surface of the black spot, but this isn’t enough to kill the growth under its protective biofilm. These deep roots survive so the spots return, even after repeated brushing and chlorine treatments. To kill black spot properly, you needs to break through that protection and kill the algae at its roots. This is what our treatment does.
How do I know if I have Black Spot Algae?
Black Spot Algae can sometimes look like copper stains. Often even pool guys get this two very different issues dead wrong. If you think you have copper stains please feel free to call us and we will help you know for sure before you uy anything.
How long do we wait before we can swim again?
You can safely use the pool again after 4 days in summer or 7 days in winter. Even though our products are safe for swimmers, during the first 7 days, the treatment is working hard to break down the Black Spot. It is best to stay out of the water during this time as the high chlorine may be uncomfortable for some swimmers.
3 Types of algae in swimming pools
GREEN ALGAE REMOVAL
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 (OR YELLOW) ALGAE
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 REMOVAL
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.
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.
