Green algae is the second most common type of algae. It tends to be more common in northern areas of the U.S. It’s a common nuisance during pool re-openings after the pool has been closed in the winter months.
Green algae is usually a symptom of long periods of low sanitizer. It’s a darker green than its counterpart yellow/mustard algae. Green algae blooms tend to be denser, and grow through out the pool.