Red tides are a natural phenomenon caused by high concentration of microscopic algae that are poisonous. The organism produces a toxin that affects the central nervous system of fish, paralyzing them. As a result, dead fish are washed ashore. They can cause human illness and deaths too, following consumption of toxic fish. When red tide algae reproduce in dense concentrations or ‘blooms’, they are visible as patches, often reddish. They occur due to temperature, salinity, and nutrients reaching certain levels, besides lack of wind and rainfall and cannot be controlled by humans. The outbreaks are commonly called red tides, though scientists prefer the term ‘harmful algal blooms’.