Lesson Plan (Grades 6–8): Aquaponics in a Bottle – Building a Closed Mini Ecosystem

Lesson Title: Aquaponics in a Bottle – Building a Closed Mini Ecosystem

Grade Level: Grades 6–8

Subject Area: Life Science (Ecology & Biogeochemical Cycles) / Chemistry (Water Quality) / Engineering Design

Overview: Aquaponics merges aquaculture (fish raising) and hydroponics (soilless plant culture) into a synergistic, sustainable system. In this hands-on, multi-week STEM project, students will design, assemble, and maintain a sealed “aquaponics in a bottle” ecosystem using a 2-liter plastic bottle, a small submersible pump, live fish, plants, and nitrifying bacteria. Over the course of four weeks, learners will monitor water-quality parameters, including pH, ammonia, nitrite, nitrate, and temperature, using aquarium test kits. They will graph trends and analyze how fish waste fuels plant growth through the nitrogen cycle. By troubleshooting imbalances (e.g., ammonia spikes), adjusting fish stocking levels or plant mass, and applying engineering principles to refine their systems, students gain deep understanding of ecological feedback loops, water chemistry, and sustainable food production. This lesson equips teachers with clear objectives, detailed materials lists, step-by-step procedures, differentiation strategies, assessment rubrics, and extension ideas to support student success.

Objectives and Standards

Learning Objectives

1. Nitrogen Cycling: Describe the conversion of fish-produced ammonia into nitrite and then nitrate by nitrifying bacteria, and explain how plants uptake nitrates as nutrients.
2. System Assembly: Construct a closed-loop aquaponics system in a 2-liter bottle, integrating a submersible pump, grow media, fish habitat, and plant bed.
3. Water-Quality Monitoring: Use test kits to measure pH (ideal 6.8–7.2), ammonia (<0.5 ppm for fish health), nitrite (<1 ppm), nitrate (5–40 ppm), and temperature (20–24 °C) twice weekly, recording values accurately.
4. Data Analysis: Plot water-quality parameters over time, identify the ammonia and nitrite peaks during system cycling, and determine when the system reaches steady state (i.e., nitrates rise and ammonia/nitrite stabilize at safe levels).
5. Engineering Iteration: Propose and implement design modifications—such as adjusting fish feeding, adding more plants, or changing flow rates—to maintain optimal water quality and ecosystem balance.
6. Sustainability Reflection: Evaluate the potential of aquaponics for sustainable, low-footprint food production in urban or resource-limited settings, connecting student systems to real-world applications.

Standards Alignment

• Next Generation Science Standards (NGSS)
  • MS-LS2-3: Develop a model to describe cycling of matter and flow of energy among living and nonliving parts of an ecosystem.
  • MS-ESS3-3: Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment.
• Common Core State Standards – Mathematics
  • 6.SP.B.5: Summarize numerical data sets in relation to their context (analyzing water-quality readings).
• NGSS Crosscutting Concepts
  • Systems and System Models: Students view fish, bacteria, plants, water, and mechanical components as an integrated system.
  • Stability and Change: Students investigate how inputs (feed, light) and outputs (waste, plant growth) interact to achieve equilibrium.