Severe (Swamp) Algae
In cases where a pool has been neglected for a long period of time, the pool itself can look like a swamp. This is a case of severe algae bloom.
Severe algae blooms can be formed from any type of algae, but usually it’s a combination of green and yellow algae. Severe black algae blooms tend to cover the surface, while green algae blooms tend to form the floating clumps on the surface of the pool.
Low water visibility can hide debris that may be at the bottom of the pool. Organic debris will use up considerable amount of chemical when attempting to turn over a pool back to clean.
Swamp pools are also common when a pool has been closed for the winter season, but wasn’t opened immediately when the weather became warm in the spring time.