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Exploring Aquaponics (Grades K-2)

Grade Level
K - 2
Purpose

Students identify the basic needs of plants and fish and engineer, assemble, maintain, and observe a small-scale aquaponics system that meets plant and fish needs. Grades K-2

Estimated Time
2 hours
Materials Needed

Engage:

Activity 1: Needs of a Plant

Activity 2: Needs of a Fish

Activity 3: Design a Classroom Aquaponics System

*A Classroom Aquaponics Kit is available for purchase from agclassroomstore.com.

Vocabulary

aquaculture: the cultivation of aquatic organisms (such as fish or shellfish) especially for food

aquaponics: a system of aquaculture in which the waste produced by farmed fish or other aquatic animals supplies nutrients for plants grown hydroponically, which in turn purify the water

decomposition: the process of breaking down or being broken down into simpler parts or substances especially by the action of living things (as bacteria or fungi)

fertilizer: any material of natural or synthetic origin that is applied to soils or plant tissues to supply one or more nutrients essential to plant growth

gills: the paired respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water and excretes carbon dioxide

hydroponics: the method of cultivating plants using a mineral nutrient solution in a water solvent without the use of soil

nutrient: a substance that provides nourishment essential for growth and the maintenance of life

photosynthesis: the process by which plants convert carbon dioxide, water, and light energy into sugars and oxygen in order to store energy; the opposite of cell respiration

respiration: the process through which a plant exchanges oxygen and carbon dioxide with its environment

spawn: release or deposit eggs

stomata: small openings in the leaves and stems of plants which can open and close to exchange oxygen and water vapor for carbon dioxide

symbiotic relationship: close, prolonged association between two or more different organisms of different species that may, but does not necessarily, benefit each member

Did You Know?
  • A wide variety of foods—lettuce, beans, broccoli, cucumbers, peas, herbs, strawberries, melons, and tomatoes, for example—all flourish through aquaponics farming.1
  • The most commonly cultured fish in commercial aquaponics are tilapia species. Channel catfish, largemouth bass, crappies, rainbow trout, pacu, carp, goldfish, perch, Arctic char, Barramundi, and Murray cod are also successfully raised in aquaponics systems.2
  • Aquaponics is featured in the Epcot Living with the Land attraction at Disney World's Epcot Center in Florida. The attraction doubles as a working lab for USDA and NASA, and the food grown there is served at the resort.3
Background Agricultural Connections

Aquaponics is the combination of aquaculture (farming fish and other aquatic organisms) and hydroponics (growing plants in water without soil). Fish and plants are simultaneously grown in an enclosed, recirculating system. A small-scale aquaponics system has ten basic components—a fish tank, a grow bed, a growing medium, a water pump, tubing, a grow light, a fish cave, water, fish, and plants. Water from the fish tank is pumped to the plants, removing the waste from the fish and keeping the fish tank clean. The fish waste is converted by bacteria into a natural fertilizer that is absorbed by the plants. The water is filtered through the plant roots and returned back to the fish tank, providing the fish with a fresh source of water. The fish and plants interact in a mutually beneficial symbiotic relationship within a single system. The waste produced by one is used by the other. With the exception of the fish food, all fish and plant needs are provided within the aquaponics system.

Plants require nutrients, water, air, and light to survive and grow. Nutrients, sometimes referred to as fertilizers, are the vitamins and minerals plants need for healthy growth. They come from the decomposition of rocks, dead plants, and animals and are absorbed through the roots of the plant. Water is also absorbed through the roots and transported to the rest of the plant through the stem. Water helps keep plants rigid and transports nutrients throughout the plant. Air enters the plant through tiny holes in the leaves called stomata. The roots absorb oxygen to convert food into energy, a process called respiration. Plants use energy from light to make food. In the photosynthesis process, the plants use energy from light, carbon dioxide from the air, and water to make sugars and starches that are used as food for the plant. In nature, plants typically get nutrients from soil, water from rain, carbon dioxide and oxygen from the air surrounding them and from air pockets in the soil, and light from the sun. In an aquaponics system, nutrients come from the fish waste, water comes from the fish tank, air is present in the classroom, and light comes from the grow light.

Like humans, fish have four basic needs—nutrients, water, air, and shelter. Different types of fish eat different types of food. Fish feed on microorganisms, smaller fish, worms, plankton, sponges, algae, aquatic plants, or commercial fish food. Freshwater fish do not actively drink water. The water they need flows into them through their gills and skin. Saltwater fish actively drink water through their mouths. Their bodies process the water to filter out the salt. Fish need oxygen from the air present in water to breathe. A fish breathes by taking water into its mouth and forcing it through its gill passages. As water passes over the thin walls of the gills, dissolved oxygen moves into the blood and travels to the cells of the fish. Fish need shelter for protection from predators. Some fish also eat, sleep, and spawn under the cover of shelters. In an aquaponics system, clean water comes from the water that is filtered by the plants and drained into the fish tank, air is present in the water, and shelter is provided by the rock cave in the fish tank. Nutrients are the only fish need that is not provided within the aquaponics system. Nutrients for the fish are added to the system, most often in the form of commercial fish food appropriate to the species of fish being raised.

Engage
  1. Ask the students, "Where is the food you eat grown?" After discussing the student responses, ask them if they think food can be grown in the middle of a big city.
  2. View the video Aquaponics – Pass the Plate.
  3. Ask the students why it might be beneficial to raise fish and plants together in one system. Use the following points to guide the discussion:
    • The fish waste is not released into the environment.
    • The waste produced by the fish is used as fertilizer for the plants.
    • The plants purify the water for the fish.
    • Food can be produced using less water than traditional growing methods. This allows food to be produced during droughts or in areas with little water.
    • Fish and vegetables can be raised at the same time.
    • Food can be produced in a small space and does not require fertile soil.
    • Food can be grown in highly populated urban areas where fertile soil is scarce.
    • Food can be produced indoors where weather and pests are less of a problem.
    • No weeding is required.
  4. Explain to the students that they are going to learn about the basic needs of plants and fish so that they will be prepared to care for them in a classroom aquaponics system that they will assemble, maintain, and observe.
Explore and Explain

Activity 1: Needs of a Plant

  1. Ask the students if they have ever taken care of a plant. If they have, ask them to describe what they did to care for their plant.
  2. Ask the students, "What are the basic needs of plants?" (nutrients, water, air, and light) Use the Needs of a Plant PowerPoint Slides to introduce the four basic needs of a plant.
  3. Divide the class into four groups. Assign each group one of the needs of a plant.
  4. Provide each group with a potted plant. The fifth plant is the "control" plant. Show the students the control plant and explain that this plant will receive everything it needs to live and grow—nutrients, water, air, and light.
  5. Each group will design an investigation to find out if their plant can survive without their assigned need. For example, if a group was assigned "light," they will design an investigation to determine if their plant can survive without light.
  6. Allow each group time to brainstorm ideas about how to design their investigation. Tell students to keep in mind that they are limited to easily available materials that can be found either in the classroom or at home. Be sure to visit with each group during the brainstorming process to give guidance and feedback. 
  7. After the necessary materials are gathered, have each group set up their investigation. Provide each student with a Plant Observation Sheet and give students time to record their observations each day for two weeks. 
  8. After the two-week observation period, have each group meet together to summarize their observations and interpret their findings. Provide time for each group to share their findings with the class. 

Activity 2: Needs of a Fish

  1. Ask the students, "What do you need to survive?" (food, water, air, and shelter) Ask the students if they think fish have the same or different needs. Discuss their responses and guide them to the understanding that fish have the same basic needs as humans.
  2. View an Ocean Live Cam. Using the information from the Background – Agricultural Connections to discuss how the needs of the fish seen in the live cam are being met.
  3. Choose a large outdoor area or gymnasium to represent the ocean. Tell the students that they are going to play "Fish Tag" and they are all fish. Assign 5-10 students to be predators. Use sports pinnies or headbands to identify the predators. Spread all of the Fish Needs Cards and the four hula hoops around the ocean. Explain to the class that the fish will have two minutes to "swim" around the ocean collecting cards while trying to avoid being caught by the predators. If a predator tags a fish, the fish has been caught and is out of the game. Eaten fish will move to the edge of the ocean and participate in an activity such as jump rope, hula hoop, jog around the ocean, etc. Each fish is trying to collect one food card, one water card, and one air card before time is up. The hula hoops represent shelter. When a fish is standing inside a hula hoop, they are safe from predators and cannot be caught. Only three fish can stand in a hula hoop at a time, and they may only stay there for ten seconds. 
  4. After one round is complete, choose new predators and play again. Repeat the game until every child has had an opportunity to be a predator.
  5. Review with the students the importance of food, water, air, and shelter to the survival of a fish.

Activity 3: Design a Classroom Aquaponics System

  1. View the video What is Aquaponics? to explore an urban aquaponics farm. Explain to the students that this farm uses a large-scale aquaponics system to produce fish and vegetables. As a class, they will be assembling a small-scale system that meets the needs of fish and plants.
  2. Project The Aquaponics Cycle diagram onto a large screen. Use the following information to discuss the cycle with the students:
    • Fish produce waste. The fish waste contains ammonia, which will poison the fish unless it is filtered out. In an aquaponics system, the water from the fish tank, including the fish waste, is pulled up to the plant trays through a pump.
    • Microbes convert waste into nutrients. The ammonia in the fish waste that is present in the water being pumped into the plant trays is quickly converted into nutrients by the bacteria naturally present in the trays.
    • Plants filter the water that returns to the fish. The nutrients are absorbed by the plants. This process filters the water. The clean water is drained back into the tank, providing a fresh source of water for the fish.
  3. Show the class the basic materials needed to assemble the classroom aquaponics system—two clear plastic containers, expanded clay pellets, water pump, tubing, grow light, fish cave, water, fish, and plants. Ask the students how they think the materials can be used to create an aquaponics system that meets the needs of the fish and the plant.
  4. Arrange the students in small groups. Incorporating the materials shown, ask each group to design an aquaponics system that meets the needs of fish and plants. Have the groups sketch their design and share their ideas with the class.
  5. After the students share their ideas, use the Classroom Aquaponics System Assembly and Maintenance Guide instructions and the Classroom Aquaponics Instructional Video to assemble the system as a class. Compare the system from the guide with the class designs.
  6. Pass out the Meeting Needs activity sheets to each student. Ask the students, "What are the basic needs of plants? (Plants need nutrients, water, air, and light.) Write the basic needs on the board and instruct students to fill in the "Plant Needs" column of the activity sheet with one of the basic needs of a plant in each row.
  7. Ask students if plants need water to come from rain, light to come from the sun, and nutrients to come from the soil. Discuss the concept that water, light, and nutrients can come from other sources.
  8. Discuss and record in the "Meeting Plant Needs" column how plant needs are met in an aquaponics system. Nutrients come from the fish waste, water comes from the fish tank, air comes from the classroom, and light comes from the grow light.
  9. Ask the students, "What are the basic needs of a fish?" (Fish need food, water, air, and shelter.) Instruct the students to fill in the "Fish Needs" column with one of the basic needs of a fish in each row.
  10. Discuss and record in the "Meeting Fish Needs" column how fish needs are met in an aquaponics system. Clean water comes from water that is filtered by the plants and drained into the fish tank, air is present in the water, and shelter is provided by the rock cave in the fish tank. Point out that food for the fish is not provided within the aquaponics system and must be provided for the fish each day. All of the fish and plant needs are taken care of within the system with the exception of food for the fish.
  11. Allow time each school day for students to feed the fish and gather, record, and interpret data in their science journals about the system's water quality, water temperature, fish behavior, and plant growth. Using the data gathered, make any adjustments necessary to maintain a balanced system.

Elaborate

  • Use the plants grown in the classroom aquaponics system in a simple recipe the students can make and taste, like the Garden Fresh Dill Dip Recipe using fresh dill and parsley.

  • Have the students make a gyotaku fish print and label the print with the parts of a fish. Follow the instructions in the activity Gyotaku: The Japanese Art of Printing Fish.

  • Make seed paper to grow plants from seed in your aquaponics system. To make the seed paper:

    • Soak eight sheets of 8.5" x 11" white paper that has been shredded and two sheets of 8.5" x 11" colored paper that has been shredded in a bowl of water for at least one hour.
    • Scoop the paper into a blender. Add two cups of the soaking water, and blend for about two minutes until you get a mushy pulp.
    • Pour the pulp through a strainer to remove some of the water. Do not squeeze all of the water out or the paper will not form together well.
    • Gently mix in the seeds.
    • Spread the dish towel out on a flat surface. Place a linen towel on top of the dish towel. The linen towel will keep the small seeds from sticking to the absorbent dish towel.
    • Spread out the pulp onto the linen towel, and flatten it down with your hand.
    • Place another linen towel and dish towel on top of the pulp, and use a rolling pin to further flatten the paper. 
    • Allow the paper to dry overnight.
    • After drying, the paper can be cut into desired shapes.
    • To plant in the classroom aquaponics system, place a small piece of seed paper into the clay pellets. 
Evaluate

After conducting these activities, review and summarize the following key concepts:

  • Nutrients, water, air, and light are the basic needs of plants.
  • Food, water, air, and shelter are the basic needs of fish.
  • Aquaponics is the combination of aquaculture and hydroponics. The waste produced by fish provides nutrients for the plants, which in turn purify the water.
  • An aquaponics system meets all the needs of fish and plants with the exception of food for the fish.
Sources
  1. https://www.usda.gov/media/blog/2013/11/8/hooked-aquaponics
  2. http://apnko.com/en/
  3. http://earth911.com/living-well-being/travel-living/epcot-living-with-the-land-the-happiest-garden-on-earth/
Acknowledgements

Classroom Aquaponics System Assembly and Maintenance Guide created by Joe Furse for the National Center for Agricultural Literacy.

Recommended Companion Resources
Author
Lynn Wallin
Organization
National Center for Agricultural Literacy
Powered by the National Agricultural Literacy Curriculum Matrix (agclassroom.org)