Algae blooms are composed of floating colonies of cyanobacteria. While New Millennium Concepts, Ltd. has not conducted specific testing for cyanobacteria, our expectation is that the reduction of cyanobacteria should occur because: Cyanobacterial cells range in size from 0.5 micrometers to 40 micrometers. A “micron” is an abbreviated term for “micrometer”, or a millionth of a meter (1/1,000,000 meters). This is about .00004 inches. For size comparison, a human red blood cell is about 5 microns across. A human hair is about 75 microns across (depending on the person).” * Working down to a smaller scale… .5-40 microns would be 500-40,000 nanometers in size. The Black Berkey Purification Elements can reduce viruses down to the nanometer scale, in the tested range of 24-26 nanometers: http://berkeywaterkb.com/is-the-ms2-fr-coliphage-still-known-to-be-a-good-indicator-of-virus-filtration-at-least-one-article-suggests-that-it-might-not-be-do-you-have-tests-on-any-other-viruses/ 24-26 nanometers is .024 to .026 microns…in other words, much smaller than cyanobacterial cells found in algae blooms. The fact that Black Berkey purification elements have been tested to remove viruses to the nanometer range suggests that contaminants much larger in size, such as cyanobacteria, should also be removed. Nevertheless, since NMCL has no specific testing for cyanobacteria, we cannot make any specific claims for cyanobacterial reduction. NMCL always recommends that you use the cleanest source of water available, whenever possible. * http://www.bacteria-world.com/how-big-micron.htm