How to Treat Algae Growth in Your Swimming Pool
Algae in the swimming pool is something that most pool owners dread seeing. Since algae loves warm, stagnant water, it is particularly likely to be a problem in a pool that is not kept at the right pH level and where the water is not circulated enough. Keeping the water ultra clean with an automatic pool cleaner can help, but even then, sometimes algae takes over.
Even though there are over 20,000 different species of algae, only one of four varieties will be found in swimming pools; green, black, pink or yellow algae. Here’s how to treat them.
- Net skim and then vacuum the pool, cleaning the filters often or backwashing sand filters as you go.
- Make sure the pH is between 7.4 and 7.6
- Late in the afternoon, sanitise the pool with trichlor at 1 gram per 25 litres of water. This will bleach dark coloured plaster pools and also vinyl pools. In these cases use liquid chlorine at 30,000 parts per million litres of water.
- Brush down all the pool surfaces thoroughly -and only after you shock the pool – whether they look like algae is on them or not. Tiny spores are invisible, but no less real. Brushing will remove the slime or the waxy coating of black algae so the trichlor can penetrate.
- Run the pool filter pump for 72 hours without stopping to thoroughly circulate the water and brush the pool surfaces once a day during this time.
- Clean the filter often to remove the dead algae
- Vacuum the pool out constantly for the same reason, cleaning the filter often, if it has one.
- After the 72 hours are up, you can go back to the normal regime of pool maintenance, but make sure the chlorine level stays at 3ppm.
Note: Using algaecides should only be done in conjunction with the above regime for the best results.
Before breathing a sigh of relief, you may have to treat more stubborn algae – black or yellow is the worst to get rid of. Do it like this: –
- Green algae – do all of the above again. If the water turns from green to blue you’ll know the algae is dead.
- Yellow algae may need a harder brushing, by hand if you can’t get enough pressure on it with the pole brush.
- Pink algae is usually fixed by the first treatment; if it’s not try doing it again while keeping the pH level between 7.2 and 7.3
- Black algae can be the worst. You need to scrub it with a wire brush then pour trichlor directly onto it. This can be tried without draining the pool in which case the trichlor will soon mix with the water and lose its strength. If that doesn’t work, you’ll need to drain the pool and do it. Sometimes an acid wash or a complete resurface is necessary.