Black algae is one of the most challenging issues to resolve in pools as it acts differently than traditional green algae. Black algae penetrate porous surfaces of pools, particularly plaster, concrete and grout, unlike floating algae. It can attach tightly because of its strong root-like structures so simple brushing or frequent chlorination treatments are not as effective.
Why Black Algae is Difficult to Remove
Black algae is a problem because it forms a protective layer that allows it to survive in poor pool conditions. The black stains on the pool surface are just one of the issues. The root system of algae can grow in small cracks and rough surfaces, making it difficult to get rid of even after it has been treated.
Common causes for black algae growth are:
- Poor water circulation
- Low sanitizer levels
- Unbalanced pool chemistry
- Infrequent brushing
- Failure to maintain for long periods of time
- Plaster surfaces that are damaged or rough.
Because the algae attach itself to the pool surface, simply adding chemicals may not completely solve the problem. This typically requires both physical and chemical treatments.
Balance and Test Your Pool Water First
If you need to treat the black algae, you should first check the pool’s chemistry. Pools that are not balanced can be difficult to treat for algae and can be a factor in algal re-growth.
Some key points to look for are:
- pH
- Alkalinity
- Sanitizer levels
- Calcium hardness
Proper alkalinity is particularly important since it helps to maintain a stable pH and water balance. If the alkalinity level is too low, it may be necessary to use a pool alkalinity increaser to stabilize the pool to continue treatment.
A balanced water treatment system will help sanitizer and algae treatment work more efficiently.
Brush Black Algae Aggressively
Breaking through the protective layer of black algae is one of the most crucial steps in reducing black algae. Algae roots need to be disrupted to allow treatment products to penetrate to a greater extent.
Use a sturdy pool brush appropriate to the type of pool for plaster pools. Firmly brush off affected areas, focusing on:
- Dark spots
- Pool corners
- Steps
- Grout lines
- Areas with poor circulation
Do not use too harsh tools which may scratch or harm the plaster finish. The purpose is to loosen the algae, but not damage the pool surface.
The algae does not return if the fish is brushed afterwards regularly.
Use the Right Pool Algaecide Treatment
If you get the job done right, a good pool algaecide can be used to help eliminate difficult algae growth. Algaecides are used specifically to control and eliminate algae problems instead of using regular cleaning products.
When treating black algae:
- Always read and observe product directions.
- Use amount recommended
- Give adequate circulation time.
- Brush affected areas (continue to brush)
Don’t put more than necessary in and don’t assume that more is better, as it can lead to further water balance problems.
The right treatment regimen and brushing will be more effective than chemical products.
Avoid Damaging Pool Plaster During Treatment
People often use “extreme” methods to remove black algae, damaging the plaster in the process. It is important to keep the surface protected due to the cost involved in making repairs to the pool.
To prevent damage to the plaster:
- Avoid hard scraping using sharp objects
- Don’t use unnecessary acid treatments.
- Ensure proper water chemistry balance.
- Only use products for the type of pool that they are intended for.
This will minimize algae growth, and help to maintain a clean, luscious pool finish.
Improve Circulation and Filtration
Black algae will regrow if water circulation and filtration are inadequate. Low flows enable contaminants to deposit and help to provide sites where algae can develop.
To improve circulation:
- Operate your pump on a regular basis.
- Change out filter as necessary
- Test return jets for proper operation
- Remove debris from the pool
A clean filter will remove dead algae particles and will help to maintain treated water circulation through the pool.
Maintain Proper Sanitizer Levels
Once a black algae is removed, it is important to keep the sanitizer levels correct to prevent regrowth. A low sanitizer level allows algae spores to survive and multiply.
Test pool water regularly and keep the sanitizer levels correct according to the type of pool and usage.
Consistent maintenance includes:
- Testing water regularly
- Modifying chemicals as necessary
- Keeping surfaces clean
- Brushing problem areas
It is easier to prevent a problem with black algae than to fix it if it happens to be serious.
Final thoughts
Removing stubborn black algae without damaging plaster requires patience, proper treatment, and consistent maintenance. Black algae penetrate into pool surfaces, so more than basic cleaning is required to completely remove it.
To protect your pool and enhance treatment results, a proper pool algaecide, balanced water chemistry and adjusting the alkalinity by adding a pool alkalinity increaser to the pool as needed may be used. There are ways to scrub away black algae, maintain your pool’s surface plaster and keep it cleaner for longer.
