Understanding Phosphates in Your Pool: What They Are and How to Keep Them Under Control

What Are Phosphates and Why Should You Care?

Phosphates are compounds containing phosphorus, and they are a natural part of the environment. You’ll find them in fertilizers, decaying leaves, pollen, even in some pool chemicals and tap water. While phosphates themselves are not harmful to swimmers, they serve as nutrient-rich fuel for algae growth.

Here’s the kicker: you can have balanced chlorine levels and still battle persistent algae if your phosphate levels are high. Algae, like any plant, thrives when there’s food available—and phosphates are its buffet. As senior editor of a leading American swimming pool publication, I’ve interviewed hundreds of industry professionals. The consensus is clear: phosphate management is essential for long-term pool health.