Blue-green algae (also known as cyanobacteria) are perhaps the most primitive living things on Earth. In response to appropriate environmental conditions, they undergo spectacular population explosions, resulting in so-called algal blooms that are toxic to a wide range of aquatic and terrestrial animals. Over the past year a deadly combination of drought, high summer temperatures, river flows lowered by withdrawals of water for irrigation, and inputs of nutrients from agriculture and townships created ideal conditions for a massive bloom of Anabaena. This article takes an extensive look at the problem of toxic algal blooms and proposes that the long-term answer may lie in better catchment and river management and the role of bio-control.