Fish pond farming – dissolved oxygen, stocking density and growth

Design & TechnologyAgriculture, Forestry & AquacultureAges 12–13

Cross-section of a tilapia pond: during the day algae photosynthesis raises dissolved oxygen, and at night fish and microorganisms respire and oxygen falls, reaching its lowest just before dawn. Students choose the stocking density, feed amount, aeration mode and weekly water-change rate, then press Run to watch the dissolved-oxygen chart for the last 48 hours, the fish mass over the days raised, and the survival rate. When oxygen drops below 3 mg/L the fish gasp at the surface and stop eating; below 1.5 mg/L they start to die — turning on the aerator or changing the water can save the pond.