Experiment 3
Stacked Container Hydroponics (Nutrient Film Technique)
Reducing waste and energy consumption is a large part of our climate change response. This experiment is geared towards utilizing food-safe containers that would otherwise be recycled, keeping their embodied energy to produce food. It is the first experiment to use a water pump and flowing water to implement the nutrient film technique. It is also the first to get more challenging in its construction. While this experiment provides a challenge, it will also provide a stable and efficient system that uses less water and less nutrients.
Step 1:
Gather the following materials and tools:
Materials
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Small food-safe strawberry plastic container
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Medium food-safe salad container
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Large food-safe salad container
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Small fountain pump (Here a 340l/h, adjustable pump was used)
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Food-safe tubing. Here 6mm (1/4") OD tubing was used with a conversion fitting (from 1/2" ID to 3/16" ID). A larger tubing will still work.
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A conversion fitting to get down to a smaller tubing size. (Seen here is a 3D printing part using PLA)
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Plumber's tape as required
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Clay pebble hydrotons
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Hydroponic Nutrient (mixed as per manufacturer's specification)
Tools
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Sharp utility knife
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Cutting board
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Permanent Marker
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TDS Meter (This is an option tool for measuring the nutrient level in the hydroponic water. This is not required if the nutrient water is replaced weekly)
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pH Tester drops/Meter (Another optional tool, this one used to measure pH levels in the nutrient water. The ideal range is a pH between 5 to 6. This is not required if the nutrient water is replaced weekly)
Step 2:
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Place medium size container onto large food container
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Using the pErmanent marker, mark outline of medium container.
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Note: The food containers tend to have tapered walls. This means the top is wider than its base. Start by cutting the opening smaller, you can adjust as needed.
Step 3 :
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Cut out the traced outline using the utility knife and cutting board.
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You may have to adjust this size as needed.
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Step 4:
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After cutting out the outline, insert the strawberry container into the lid to ensure everything fits properly.
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Assemble the lid onto the container for the next step.
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Step 5:
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With the lid & strawberry container attached to the medium size container, trace a flap outline. The bottom of the flap should be about halfway down the strawberry container.
Step 6:
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Carefully cut out flap outline. Ensure the Ensure the bottom line does not get cut, so the flap remains attached to the container.
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Fold down flap outwards.
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Step 7:
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Stack the medium size container over the large container.
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Line up the containers so the medium container is in the middle of the large container.
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Using the marker, outline an opening to be cut out to allow the water to flow back into the large container
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Step 8:
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Cut out the outline. Ensure the opening is tight to the medium container.
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Note: Once the water pump is running and water flowing through, adjustments may be needed to ensure that water is directed perfectly through this opening. The flap may need to be cut shorter and the opening cut larger.
Step 9:
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If a conversion fitting is required, assemble it with the pump.
- Use plumber's tape as required.
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Note: If you have access to a 3D printer, you can use the following link to access the conversion fitting created for this project:
Step 10:
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Place the water pump into the large container. Feed the power cable through the cut opening.
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Ensure the water pump is placed at the opposite end from the opening.
Step 11:
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Mark out location for a hole where the water line will run through the lid and into the top container.
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Step 12:
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Using the utility knife, cut out the hole.
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Note: A snug fit is better than a loose fit in this case. This will help the pump remain upright when the experiment is moved around.
Step 12:
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Feed the tube through the opening and attach it to the pump.
Step 13:
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Mark another hole to be cut on the top container. Again, a tighter fit will prevent everything from coming lose.
- Cut out marked hole
- Cut the tube down to size
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Note: Ensure that the tube is long enough to prevent it from kinking, which would put additional strain on the pump and reduce the water flow.
Step 14 (optional):
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As an optional step, place adhesive strips at the bottom of the small container to keep it in place over the large container.
Step 15:
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Assemble all containers together.
Step 16:
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Fill the strawberry container with the clay hydrotons up to the edge of the container.
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Fill the large container with hydroponic nutrient water. While the system is running, top of the water as needed.
Step 17:
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Place seeds or seedlings into the hydrotons.
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Place the containers near a window or under a grow light.
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Monitor the nutrient water using the TDS Meter and pH tester. Add more nutrient one it drops below recommended levels. Add pH up or pH down to balance pH level as required. Alternatively, replace the nutrient water weekly,
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If algae or mould form, carefully remove the plant, clean the all parts with soap and water, and replace the nutrient water. You can also add in 3% hydrogen peroxide (10ml per gallon/ 4 litres, up to 3 times per week).
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Note: If you are growing in the winter where natural light is reduced, you will need to use a grow light to ensure the plant is getting the light it needs. On average plants need 6 to 8 hours of direct sunlight. For best results provide 12 to 16 hours of exposure to a full spectrum grow light.