What causes Algae problems?

Every pool owner has, at one time or another, done battle with the occasional algae bloom. Algae spores constantly enter the pool, brought in by wind, rain or even contaminated swimsuits or equipment. When conditions are right, an algae bloom can occur seemingly overnight. These conditions include out of balance water, warm temperatures, sunlight and presence of nitrates and/or carbon dioxide. Of course, a lack of proper circulation, filtration and sanitation may be the primary cause of the algae. The best process is one of elimination.

Algae is a living aquatic creature that multiplies rapidly on warm, sunny days. Containing chlorophyll, algae utilizes photosynthesis to grow. That is, they take in carbon dioxide and expend oxygen as a byproduct.

A thunderstorm will sometimes turn an outdoor swimming pool green; this article tells you why.
It’s all about the nitrogen.

Thunderstorms have lightning and rain as well as a few resounding claps of thunder.
The flashes of lightning, apart from lighting up a night sky, create nitrogen in the atmosphere and the rain washes that nitrogen down and into your pool.
Nitrogen is a plant food, and a very good one. The algae in your pool, and there are always traces in even the best maintained pool, are plants and so they thrive on the extra nitrogen that is washed down when the heavens open.
Algae are microscopic and so, when there are just a few of them, they are invisible to the human eye but feeding on the nitrogen, they bloom and multiply very quickly until there are enough to turn the pool water green and murky.