Lesson 4: Comparative Growth and Nutrient Analysis
Duration of Days: 6
Lesson Objective
Students will conduct a controlled comparison of plant growth in aquaponic water, tap water, and lightly fertilized water, and evaluate aquaponics as a productive and sustainable system.
Does aquaponic water support plant growth effectively?
How does fertilized water compare in short-term growth?
Does plant integration reduce nitrate levels in the tank?
Which system is most sustainable long term?
Control group
Experimental group
Independent variable
Dependent variable
Fertilizer solution
Biomass
Growth rate
Sustainability
Yield
HS-LS2-4
Use mathematical representations to support claims for cycling of matter.
HS-ETS1-3
Evaluate solutions based on prioritized criteria and trade-offs.
Science and Engineering Practice – Planning and Carrying Out Investigations
Science and Engineering Practice – Analyzing and Interpreting Data
Crosscutting Concept – Energy and Matter
Crosscutting Concept – Stability and Change
Students analyze comparative data.
Students interpret experimental outcomes.
Students evaluate sustainability claims using evidence.
Day 1 – Experimental Setup
Students establish three growth conditions:
Aquaponic water
Tap water
Lightly fertilized water
They standardize:
Plant species
Container size
Light exposure
Initial plant size
Students define:
Independent variable – Water source
Dependent variable – Plant growth
Purpose of Day 1
Reinforce experimental control principles.
Day 2 – Initial Measurement
Students measure:
Initial height
Leaf count
Color
Root appearance
Baseline nitrate in aquaponic system is recorded.
Day 3–4 – Ongoing Monitoring
Students measure growth parameters.
They observe:
Rate of growth
Leaf coloration
Root development
Water clarity
Simultaneously, students monitor nitrate levels in the aquaponic tank.
They begin identifying trends:
Is nitrate decreasing?
Is algae changing?
Day 5 – Comparative Data Analysis
Students construct:
Comparative data table
Simple graph of growth across conditions
They answer:
Which condition produced fastest growth?
Which appears most sustainable?
Does fertilizer outperform aquaponics short term?
What are trade-offs of fertilizer dependency?
Day 6 – System Evaluation Reflection
Students evaluate:
Is aquaponics competitive with fertilized systems?
Does aquaponics reduce nitrate effectively?
How does sustainability compare?
Purpose of Segment
Students move from stabilization to productivity evaluation.
DOK Level
DOK 2
Record and compare growth data.
DOK 3
Evaluate competing systems using evidence and sustainability reasoning.
Approaches DOK 4
When students synthesize growth data with nitrate reduction trends and defend sustainability claims.
Industrial agriculture relies heavily on fertilizer.
Excess fertilizer runoff causes water pollution.
Sustainable agriculture seeks closed-loop alternatives.
Students connect aquaponics to environmental stewardship and food access.
Fertilizer superiority means aquaponics is ineffective.
Short-term growth determines long-term sustainability.
More growth automatically equals better system.
Provide pre-made data tables.
Allow graphing by hand or digitally.
Offer structured comparison prompts.
Challenge advanced students to analyze nutrient efficiency ratio.
Comparative Analysis Write-Up
Students submit:
Data table
One graph
Written evaluation comparing growth and sustainability
Assessment emphasizes reasoning, not perfect plant growth.