What You Need to Know About Algaecide for Swimming Pools

Keeping your swimming pool clear and safe requires more than just chlorine. One of the biggest threats to water quality is algae growth. Without proper treatment, algae can turn the water green, make pool walls slippery, and create an environment for harmful bacteria. This is where algaecides come in.

In this article, we explain what algaecide is, the types of pool algae, the pros and cons of different algaecides, and the best practices for using them.

Why Algae Is a Problem in Swimming Pools

When a pool is left idle for some time, algae may begin to grow. This can cause the water to:

Turn green or cloudy

Develop slimy spots along pool walls and the waterline

Consume free chlorine, making sanitization less effective

Provide a breeding ground for bacteria

If you want to swim in clear, safe water, regular pool maintenance is essential. Using an algaecide as part of your routine can help prevent algae growth, while shock treatments are often needed to eliminate existing infestations.

Common Types of Pool Algae

1. Green Algae

The most common form of pool algae. It floats freely in the water, turning it green, or attaches to the walls and floor, making surfaces slippery.

2. Yellow Algae (Mustard Algae)

Grows in shaded areas of the pool and appears as yellow, golden, or brown-green spots. It is more chlorine-resistant than green algae.

3. Black Algae

The most difficult algae to remove. Appears as black or blue-black spots on pool walls, often in tile grout or cracks. It resists chlorine and most algaecides, requiring strong chlorine shock and scrubbing. Sometimes, rubbing a trichlor tablet directly on the spot is effective.

4. Cyanobacteria (Blue-Green Algae)

Technically bacteria, but commonly referred to as algae. It forms floating filaments and can quickly cause large-scale blooms. Cyanobacteria are especially resistant to treatment.

How Algaecides Work

The principle behind algaecides is to disrupt algae’s physiological functions, such as cell division and photosynthesis, ultimately causing the algae to die.

However, algaecides work slowly and are primarily used as a preventive measure. For effective algae control:

Keep free chlorine levels between 1–3 ppm

Use algaecide regularly to suppress algae formation

Apply chlorine shock if algae growth is already visible

Types of Algaecides and Their Pros & Cons

Chelated Copper Algaecide

Appearance: Blue or blue-purple liquid with a slight ammonia odor

Advantages: Low cost, highly effective, suitable for winterizing pools

Disadvantages: Toxic if pool water is ingested, may cause scaling or staining, and often takes 24 hours or more to work

Polyquaternary Ammonium Algaecide (Polyquat)

Examples: WSCP and APCA

Appearance: Light yellow liquid

Advantages: Non-toxic, non-foaming, does not stain or scale; ideal for regular algae prevention

Disadvantages: Works best as a preventive solution; if algae bloom has started, chlorine shock is still required

Best Practices for Using Algaecides

Use algaecide preventively, especially during hot weather or after heavy pool use

Shock the pool before or after algaecide treatment if algae is already visible

Brush pool walls and floor to improve effectiveness and prevent algae from clinging to surfaces

Maintain water balance (pH 7.2–7.6, chlorine 1–3 ppm) for best results

Algaecides are a valuable tool for keeping your swimming pool clean, clear, and safe. While they are not a quick solution for heavy algae blooms, regular use can prevent algae from becoming a problem in the first place.

At Yuncang, we supply a full range of algaecides, including copper-based and polyquat-based formulations, as well as other pool chemicals like chlorine tablets, pH regulators, and shock treatments. Our products are manufactured under strict quality standards and exported worldwide.