Algae buildup is often normal, depending on climate changes and maintenance schedule. However, with too many phosphates in the pool, algae can build up quickly. Unfortunately, this type of algae buildup is not simply treatable with just algaecide, as it's very stubborn.

Phosphates feed algae, making it grow and spread out of control. While you cannot completely eliminate phosphates from your water, you can make a few changes to limit what enters your pool. To treat and prevent this, you must first understand what causes phosphates in your water.

Weather

Storms can blow rain water, leaves, dirt, and other debris into your pool.

Beauty Products

Makeup and hair care products are the biggest culprit here. Perfumes, lotions, and sunscreen are also to blame.

Fertilizers & Soil

Running from the grass into the pool can track lawn treatments into the water. Soil is home to phosphates as well so dirt and mud are also major causes.

Now that we know some of the major causes, we can look at treatment and prevention of such issues.

Weather

Try to keep your pool covered when not in use. Do your best to clean, treat, and vacuum after every storm or windy day.

Beauty Products

Ask guests to shower or hose off before entering the pool. Not everyone will be a fan of this rule, but once you explain what beauty products can do to your pool they'll understand. Sunscreen is unavoidable however. What you CAN do is make sure it's thoroughly rubbed into the skin, and make sure to use as little as possible (only as much as necessary for safety)

Fertilizers & Soil

Keep a hose or shower by the water and request swimmers wash their feet before every entry. It might be mildly irritating to excited kids, but it will make a big difference.