Single-celled organisms that include seaweed, many fresh-water plants, and certain opportunistic pathogens such as Prototheca.
Microscopic plant-like organisms that contain chlorophyll. Algae are nourished by carbon and use sunlight to carry out photosynthesis. They are introduced by rain or wind and grow in colonies producing nuisance masses. Algae are not disease-causing but they can harbor bacteria and they are slippery. There are 21,000 known species of algae. The most common pool types are black, blue-green, green and yellow or mustard. Pink or red colored algae-like organisms exist but are bacteria and not algae. Maintaining proper sanitizer levels, shocking and superchlorination will prevent their occurrence.
A group of non-vascular aquatic plants, most of which have chlorophyll; often referred to interchangeably as phytoplankton.