Students often have difficulty grasping the complexity of ecosystems and the importance of biodiversity. The following activity applies students’ creativity and basic math skills to creating a sustainable and diverse food web. The biological budget activity ties together numerous ecological concepts (structure of a food web, diversity and interdependence of organisms, and transfer of energy through an ecosystem), making it a great way to review concepts and terminology for an ecosystem unit (NRC 1996). The ecosystems represented in this version of the biological budget are coral reefs, mangrove forests, and seagrass beds.