Exploring Aquaponics for High School
Easy Do-at-Home Activity
The students will identify and understand how of plants and fish work together in an aquaponics system through the engineering, assembly, maintenance, and observation of a small-scale aquaponics system.
As the global population grows, simultaneously the amount of available farmland decreases. The challenge of feeding more individuals on less land becomes very real and relevant. Aquaponics presents one possible solution to this situation as it incorporates both plants and animals into one system and leaves little waste.
Aquaponics is one sustainable method of agriculture. There is some input and maintenance with the aquaponics system such as cleaning filters and feeding the fish. Aquaponics systems are environmentally responsible with lower water usage and relatively low power usage. In this lesson, you will use the “Water Garden” kit from Back to the Roots provided by Oregon Agriculture in the Classroom to investigate different aspects of an aquaponics growing system. Specifically, students will be investigating the question: Is farming without soil one viable method to help meet the growing food needs of the world?
- Ask your students to imagine a farm. What things are on the farm? Possible answers include: animals, plants, tractors/equipment, land. Record responses on the board (or create a poll if virtual).
- What about when space is a problem, then what can we do?
- Students will take a couple minutes to research what it looks like to farm without using land. What methods exist? One method is aquaponics. Introduce the concept and ask students to explain what they think it means.
Aquaponics- art of growing plants in nutrient rich water—those nutrients are provided by the fish. This method uses less water and land than traditional agriculture. This is a benefit because farmland is limited. Often the fish provide a protein source as well, which relieves pressure on ocean fisheries. Once established, a symbiotic relationship is developed and the only input is food for the fish!
Activity 1: Looking into Commercial Aquaponics Systems
There are two basic ideas coming together for aquaponics—growing plants without soil and raising fish. This differs from hydroponics which does not include fish.
- What does running a successful aquaponics operation look like? Let’s take a tour of a successful aquaponics operation. Questions to consider:
- a) What purpose do the fish serve?
- b) Which species of fish do they use?
- c) Does water move around? Why or why not?
- d) What similarities and differences do you see between the kit in our class and the more commercial version?
- The class aquaponics unit is a small scale version of what we saw. Have the students create a venn diagram of attributes from the two systems with similarities in the center. This can be done together as a Google Jamboard or in person on a whiteboard.
Activity 2: Looking Deeper at Water, Nitrogen Cycle and Fish
No matter the size of the system there are needs to consider for every living creature. This section we will look at the needs of plants and examine the role fish play in understanding the nitrogen cycle.
All plants are critical for sustaining life in humans and animals. This covers everything from fruit trees, nuts, leafy green, and herbs that we may grow in our Aquaponics system.
- Have your students use the needs of plants worksheet to figure out the needs of a plant.
- Figure out what the four broad categories at the top are then sort the rest of the information into those categories.
- After complete, discuss how the plant is able to meet all its needs in this Aquaponics system.
- What,if any, adjustments need to be made compared if you were growing these plants with soil.
- Are there any needs you would add for plants in an Aquaponics system
- Is taking care of plants easier, more difficult or the same?
Nitrogen Cycle and Fish Working Together
Many of the world’s resources are not available for use by plants or animals: only one percent of the Earth’s water is drinkable. Two percent of the water on earth is glacier ice at the North and South Poles. Although 80 percent of the Earth’s atmosphere is made of nitrogen—this form (N or nitrogen gas) is unusable by plants. Today we’re going to experience how nitrogen changes its molecular form during the Nitrogen Cycle and learn what forms can be assimilated by plants.
- Have students brainstorm reasons why the other 99 percent might not be available for consumption. Record answers on the board. After some time, explain that 97 percent of water on Earth is salt water. Similar to the availability of water, some plant nutrients are not easily used by plants. Plants need nitrogen but a lot of the available nitrogen is used by them. How is it Used?
- Students will discover more about the Nitrogen Cycle through filling in the missing pieces of the Nitrogen Cycle Diagram to the left, The complete cycle found here. They can research the cycle further if they can not fill in everything.
- Have students create a nitrogen cycle diagram for an aquaponics system using the aquaponics system (example). Ask key questions:
- Is this an improvement for the environment?
- How do the circles at the bottom compare. Do they change in relevant size?
- Bonus: What is the equation of the nitrogen cycle?
Aquaponics uses this information and is an excellent resource for teaching the Nitrogen Cycle. First, fish in an operating aquarium are fed. Second, fish excrete ammonia and solid waste that is converted by bacteria in the system to ammonia. Even low levels of ammonia are toxic to fish. If ammonia builds up in the tank, the fish may die. Third, beneficial nitrifying bacteria convert the ammonia to less toxic nitrate, which is readily absorbed by the plants growing in the grow tray. By cycling the ammonia and nitrate filled water to the plants, the plants remove these forms of the nitrogen from the water, and use them to grow. Fourth, the water then filters down through the grow tray and returns to the tank, giving the fish fresh clean water to live in.
Activity 3: Testing Nitrogen in the Classroom
- Prior to adding fish to the system, use your test kit to measure the levels of ammonia (NH3), nitrite (NO2), and nitrate (NO3) in the tank and record the amounts in your table.
- Add fish to the system. It recommended to start with just one beta fish but you can experiment with this or try one round with beta and another with goldish. Once the initial cycle is stable, add a few more and continue to add fish incrementally until you have an adequate bioload (generalised term for the amount of life existing in an aquarium) for the system.
Information on Bioload:
- If the bioload is creating more waste than your system can handle, then the Nitrogen Cycle is out of balance, leading to problems in your aquarium.The bioload in your aquarium is too high when ammonia and nitrites are being produced faster than the bacteria in your filter can convert them to nitrates.
- Fortunately, this is easy to test, since ammonia and nitrite levels should be 0 ppm. Any indications of ammonia or nitrites –after your tank has cycled– could clue you in that the bioload is too large for your aquarium. If this is the case, you have two options:
- Get a larger filter or
- Get rid of some fish.
- Measure NH3, NO2, NO3, and pH levels of the water that the fish came in, recorded on your table
- If you need any reference on setting up your unit please use this video.
Day 2 +
- Measure NH3, NO2, NO3, and pH levels of the Back to the Roots aquarium water and record on your table. Virtually, the instructor could provide photos of the results of strip readings and allow students to analyze and record the results.
- Repeat the four tests 2-3 times a week for the next three or four weeks. Make sure to run the tests at the same time daily, before the fish are fed. The initial cycle will be completed when ammonia (NH3) and nitrite (NO2) levels are both at zero. These testing kits are common and can be reordered inexpensively online.
- Record results using the above grid or have the students create a spreadsheet.
- After several days of data have been collected, have the students graph the results.
- Review the information displayed on the graphs. Is there a baseline to compare it to?
- Ask students to look up levels for a large school operation through research on the internet or making contact with a nearby industry.
After testing is complete and you and your classroom feel comfortable with the system, use it to grow some herbs, leafy greens or sprouts.
- Students design a sustainable system within the given budget, that is practical, easy to maintain, and allows for scalable food production. All students should review aquaponic system types and decide as a group which system best fits the needs of this project. Separate into groups and research a specific topic while aligning ideas with other group decisions. Present topic to classmates and submit group design proposals.
Criteria to evaluate
- Water Management
- Aquaponics System
- Divide students into groups of 3-4. They will write a sketch based on what they learned about the Nitrogen Cycle.
- Use keywords in their sketch– consumers, producers, nitrates, bacteria, air, soil, nitrogen fixation, plants, animals.
- The sketch should be a situation that incorporates how the cycle happens from the Plant perspective or Fish Perspective. The more abstract the situation, the more exciting.
- Have students read their stories out loud or act out if possible.