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 3-5

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

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 transport 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, 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 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.

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. Show 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.

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. Distribute the What Do Plants Need to Grow? grid and cards to each student.
4. Instruct the students to cut out the cards and place them on the grid in the column under the plant necessity described and the row number indicated on the card.
5. After the students have arranged all of their cards, review the PowerPoint to check that the cards have been properly placed on the grid.
6. Once the students are satisfied with the arrangement of their cards, instruct them to tape the cards together exactly how they are placed on the grid, being careful not to tape them to the grid below.
7. When all of the card pieces have been taped together, ask the students to turn the cards over to reveal the diagram of the needs of a plant. Using the information from the PowerPoint and the cards, discuss the basic needs of a plant.

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. Organize the students into small groups to play the game "Go Fishing." This game is played like the game "Memory," but instead of trying to find exact matches, the teams will match questions about the basic needs of fish with the correct answers. Provide each group with a set of Go Fishing Cards, paper clips, a pencil, a piece of string, and a magnet. The cards should be printed with the fish picture on one side and the words on the other.
3. Instruct the groups to make their fishing pole by tying one end of the string to a pencil and the other end to a magnet. They should attach a paper clip to each card and spread them out with the fish images facing up.
4. Split the groups into two teams. The teams should take turns "catching" two fish cards with the fishing pole. If their fish cards match, they keep the cards and take an extra turn. The cards match if one card correctly answers the other card's question. After all of the cards have been correctly matched, the team with the most matches wins.
5. After the game, review the basic needs of a fish by discussing the questions from the cards with the class.

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 nitrite and nitrate by the bacteria naturally present in the trays.
   • Plants filter the water that returns to the fish. Nitrates and nitrites are beneficial nutrients that 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.
4. Arrange the students in small groups. Incorporating the materials shown, ask each group to design an aquaponics system that meets the needs of the 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.) Instruct the students to fill in the "Plants Needs" columns 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 adjustments as necessary to maintain a balanced system.

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 of the needs of fish and plants with the exception of food for the fish.

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/

• Activity 1 was adapted from the lesson What Do Plants Need to Grow? created by the California Foundation for Agriculture in the Classroom.
• Classroom Aquaponics System Assembly and Maintenance Guide created by Joe Furse for the National Center for Agricultural Literacy.

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