Assess students' ability to design a closed-loop aquaponics system capable of sustainably supplying year‑round vegetables and fish for a family of four. Require a schematic and calculated justification covering biological nutrient cycles (ammonia → nitrite → nitrate, plant uptake, solids breakdown), tank and grow‑bed sizing (stocking densities, feed conversion ratios, crop area and yields), water and energy budgets (daily/annual flow, heating, pumps, lighting), filtration and aeration systems (mechanical, biological, media/clarifiers, oxygenation), monitoring/control strategies, and contingency/failure modes with mitigation and recovery plans. Students must state assumptions, show all calculations, and discuss trade-offs for resilience and sustainability.