Researchers have an enhanced understanding of a common freshwater alga and its remarkable ability to remove strontium from water. Insight into this mechanism ultimately could help scientists design methods to remove radioactive strontium from existing nuclear waste. They are the first to show quantitatively how Closterium moniliferum sequesters strontium (in the form of barium-strontium-sulfate crystals) and to use this to think about a practical sequestration system for nuclear waste that maximizes strontium removal.