If algae grows in your pool after rain, you're not alone. Today, we'll go deeper into why algae grows in the first place, and how rain expedites the process.

What is Algae?

Algae is a microscopic "plant" and is usually green in color (yellow algae is another one. Black algae is not algae, but bacteria). Algae spores come from surrounding environment and are brought into the pool by winds, or they can already be present in the water you filled the pool with.

How does algae grow?

Algae, like most plants, require nutrients, sunlight, and water to grow. Build up of nutrients (usually phosphorus and nitrogen) lead to faster algae growth. They come from sources like fertilizers, human waste (pee, poop, sweat), grass, leaves, trees, bugs, etc.

Poor water circulation, low chlorine, and abnormal pH levels are also factors that lead to algae growth in the pool.

How does rain expedite algae growth?

Rain is an excellent absorbent. When these droplets fall, they absorb carbon dioxide, and dust in the air. Most algae strains needs carbon dioxide for photosynthesis. Also, winds accompanying the rain bring in nutrients from the surrounding environment (nearby trees, farms, oceans). This quick access of food source is a major factor for algae growth. 

Rain also fills the pool with more water, diluting the existing chlorine concentration in the pool. This reduces chlorine's killing efficiency.

Depending on the environment, rain will either decrease or increase the pH in the pool. Either way, algae will grow in the pool.

What to do about it?

Now that we know how rain expedites algae growth in the pool, we can tackle each problem accordingly:

1. Rain decreases chlorine level: increase chlorine concentration to 10ppm immediately. Extremely high concentration stops algae growth by killing it. You can use this calculator to compute for chlorine concentration based on your pool volume. We always recommend to use high quality chlorine.

2. Low pH / High pH: low pH is excellent for improving chlorine's efficiency. If this is the case, simply add chlorine into the pool. If it is high pH, lower it down immediately to 7.2 after it has stopped raining to improve chlorine's killing power. You can use this calculator to know the exact dosage of acid required to bring pH down.

3. Nutrients: nutrients are a feast for algae. But there are products like phosphate binders or special clarifiers that can coat these nutrients, blocking the access of algae to its food source. Phosphate binders can be found in most aquarium shops. We've also created one called IwNite Hybrid Algae Preventer. Special clarifiers that contain phosphate binders can also control nutrients. They are cheaper than phosphate binders. When buying a clarifier, ask the shop for one that contains phosphate binders. Clear-Up Clarifier is our choice.

One Special Chemical that we add to our pools is Spark Pool Conditioner. It prevents algae by not allowing it to form an outer protective layer. This allows chlorine to kill algae at a relatively small concentration. Just one dosage can last for up to 12 months, making it an ultimate algae preventer. Click here for more details. 

Do these steps and algae will dare not touch your pool after rains. Thank you for your attention.