Algae are small plants growing in water, very fast in warm sunny areas. There are numerous kinds of algae that usually develop in pools, for example, green, mustard, and black algae.
Green Algae: The most common type, green algae floats in the water and can turn your pool green almost overnight.
Yellow/Mustard Algae: More stubborn than green algae, yellow algae sticks to pool walls and floors, making it harder to remove.
Black Algae: The toughest of all, black algae forms in cracks and crevices and has a protective layer that makes it resistant to chemical treatments.
Each one comes with its problems, but they all share one common feature- fast reproduction in case not handled properly.