According to WebMD, aphanizomenon flos-aquae is a kind of blue-green algae, or cyanobacteria, that is used for many treatments and supplements. There is not any scientific evidence to prove its effectiveness.
According to WebMD, the uses for blue-green algae include reducing allergy symptoms, treating arsenic poisoning, attention deficit hyperactivity disorder, twitching eyelids, fatigue, diabetes, hepatitis C, high cholesterol, malnutrition, menopausal symptoms, precancerous mouth sores, premenstrual syndrome, anxiety, depression, heart disease, wounds and digestion problems. In addition, it has been used as a dietary supplement for exercise performance, weight loss, dietary protein, vitamin B12 and iron.
According to Wikipedia, aphanizomenon flos-aquae is a freshwater species of cyanobacteria. It has both toxic and non-toxic forms, but most sources in the world are toxic because they contain hepatic and neuroendotoxins. According to the US National Library of Medicine, aphanizomenon flos-aquae is harvested from natural blooms in Klamath Lake in Oregon. The algae produces a toxin, microcystin, which has the potential to be dangerous if too much is consumed. WebMD states that blue-green algae products contaminated with these toxins are especially unsafe for young children and have been known to cause liver damage, stomach pain, nausea, vomiting, weakness, thirst, rapid heartbeat, shock and death.