TIC Hydroponics

designed for the NYC and NYC Watersheds TIC Program
presented at the 2009 NY Fall TIC Conference
conceived and written by Janine Guadagno, TIC teacher

first example by Tom Lewoc, TIC teacher
second example by Nick Gastelecutto, TIC teacher

Through these lessons, students will understand how plants and animals work together in an ecosystem to provide nutrients and dispose of waste.  In particular students will be able the monitor the ammonia/nitrogen cycle.

The clean, cold, fresh water streams in New York City are an excellent ecosystem for many different species including trout.  These streams however have limits to the amounts of waste and uses it can support before the system is overloaded.  By creating a similar ecosystem using the trout tank and hydroponics, students will see that natural ecosystems, if monitored, can support many diverse uses.

green and yellow post-it notes, drawing of a stream, TIC tank, UV light, plant seeds, styrofoam board, nitrogen (ammonia, nitrate, nitrite) testing kits.

1. Draw a picture of a mountain stream on the Board.  Provide each student group two sets of colored post-it notes.  Ask them to put down name of things that are living (biotic) on the green notes and names of things that are nonliving (abiotic) on the yellow notes.  Invite the students to come and place the notes on the drawing of the stream and discuss why they think it is found in this ecosystem.  If needed prompt the students to place wastes - both natural (ammonia) and other on the board.  Identify how the nitrogen cycle uses aquatic organism waste to feed the plants.

2.  Set-up the trout tank and begin monitoring the ammonia levels. As the levels begin to rise and the pH begins to drop, discuss how the natural stream system would handle the waste.  There is some flushing (simulated by water changes) but plants are the natural recyclers of the ammonia.  Have the students research the nitrogen cycle and identify how it could be simulated in the trout tank.

3.  Have the student research plants that could be grown hydroponically in the tank conditions - temp will be a limiting factor as well as light.  Purchase an overhead UV light to add light to the tank unless it is directly in front of a large window.

4.  Cut a piece of Styrofoam to fit the top of the tank and float just inside.  Cut small plugs out of the Styrofoam and insert aquaplugs into each.  Drop in the seed (lettuce works best), provide light and let the plants grow.

5.  Continue to monitor the tank pH and ammonia and measure the impact the plants make as they grow.

Research the benefits of aquatic plants and their impact on the global ecosystem.

One Example

from Tom Lewoc, TIC teacher in Connecticut

    Essentially, it is a 10 gallon fish tank with a plexi glass cover and a grow light.  I actually bought this set at a tag sale where the individual was selling an old tank with a hood and a light.  Here is the easiest and most cost efficient way that I have been able to modify hydroponics for the classroom: 

    As far as the seeds, I have the students place a (tomato, basil, or radish) seed into a ball of cotton (the roots grow very easily through the cotton).  Next I cut a 5x5 inch piece of pink insulation board (it floats, it’s cheap, it’s easy to cut out, and typically there is some left over from the initial tank setup.) and encompass the seed/cotton ball into a ½ inch hole cut through the board.  From there, we fill the tank with approx 3 inches of used fishtank water (emptied during a water change) and float the boards.  As long as the bottom of the cotton is in contact with the water you let nature do it’s work.  And if a few weeks you have sprouts, then gorgeous white roots, and finally mature plants.  In years past we have also started the seeds in a petri dish and a layer of cotton.  As long as you keep the temp and humidity up you should have no problems.  Replenish the water when ever you do a water change and the plants grow amazingly well in the high nitrate environment.


Another example
from Nick Gastelecutto, TIC teacher in Idaho

Some keys to this are:
1. using low nutrient requiring plants, I used thai basil and bibb lettuce
2. start running the system when you set up your tank to germinate the seeds and have some root growth before the eggs hatch (4weeks prior to recieving fish worked perfect last year).  I hung an aquarium florescent light above the box to help with the limited winter sunlight.
3. use a well washed (I bleached and thoroughly rinsed) nuetral medium in the filter box (I used rock and pumice because I had it on hand) you could use a clay medium like hydroton, so that you don't add any unaccounted for nutrients or toxins into the system.
4. I have the pump on a 6$ timer, to start with I had the pump on 24hrs to germinate the seeds.  After there is growth you can adjust how long you want the pump on depending on the student testing of Nitrates in the water.  I continually have to adjust the time its on to account for the growing roots (filter)
5. The pump I use was 25$ and is called the littleGIANT, 8 watt, 77 gal/hr pump.  It doesn't put out near 77 gal/hr though.
6. I would suggest still using a water filter because that isn't actually taking out the nitrates, it helps with DO, and it aids in the fixation of ammonium and nitrite.  This aquaponics filter really limits the need for water changes however and creates a more natural ecosystem to teach from/about.
7. I get in to photosynthesis, ecological relationships, sustainable farming practices, and food production with this.

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