What Causes Red Algae in Swimming Pools?

The sight of a clear, sparkling pool is one of the greatest joys of summer. The sight of discolored, ugly algae on your water is the quickest way to end the pool party. A pool that becomes infested with algae offers no joy at all. Find out what causes red algae in swimming pools, and learn how to deal with it and prevent it.

Clear blue swimming pool all ready for summertime.

Red Algae in Swimming Pools

Red algae appears on the surface of pool water as small, rust-colored specks or larger, pink patches floating on top of the water. Get rid of red algae in swimming pools with a chemical shock treatment. Introducing chlorine into the pool water usually kills algae, but this may not work with red algae for one very good reason: Red algae is not actually algae at all. The red specks found in swimming pools look like red algae and are usually called red algae, but the substance is actually a type of bacteria in the water.


Algae is transferred into pools by wind and rain, flourishing under sunlight and creating bacteria in the water. The bacteria commonly called red algae may contain pathogens which create disease. Bacteria grows in unclean water that isn't properly sanitized. Regular swimming and exposure to wind and rain may cause bacteria buildup in pools. Prevent the growth of bacteria in swimming pools by adding chlorine, bromine or other nontoxic disinfectants to the water.

Real Red Algae

Real red algae does exist and is sometimes found in salt- and freshwater aquarium environments. Often red algae is introduced into the system through plants and fish that are added to the aquarium. The red algae found in aquariums is not the same bacteria found in swimming pool water.