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Building and Using a
Hydroponic/Aquaculture System in the Classroom

By Ernest Nicol



TYPE OF ACTIVITY:

  • Construction Project
  • Hands-on Activities

TARGET AUDIENCE:

  • Life Science
  • Biology
  • Environmental Science

BACKGROUND INFORMATION:

Two helpful references related to this project:
  1. Jones,L. (1977), Home hydroponics and how to do it! New York: Crown Publishers
  2. Nicol, E. (1990), "Hydroponics and Aquaculture in the High School Classroom" , The American Biology Teacher, Vol. 52 No.3 March 1990.


LESSON / ACTIVITY

The following are the details for constructing a hydroponic / aquaculture system for your classroom. I have used the apparatus for the past six years in my class with excellent results. A 100 gallon aquarium serves as our fish farm. Teams of students monitor the change in biomass of the fish population, (usually Tilapia).They also maintain records of the amount of high protein floating fish food consumed. As aquaculturist they try to develop a feeding regime that will maximize the fishes growth.

Water from this tank containing the fishes' metabolic wastes is pumped every thirty minutes through a series of five hydroponic tubes filled with lava rock. Seedlings in Jiffy 7 peat pots are inserted into circular holes in the tubes. This soiless garden can support about forty plants.We have grown many varieties of lettuce, spinach, herbs, tomatoes, cucumbers, jalapeno peppers,as well as many types of flowers. In addition,climbing plants such as morning glories or four o'clocks or nasturtia are grown directly from the surface of the aquarium by inserting Jiffy 7 pots into floating styrofoam. These are supported so they arch across the ceiling.

Unless there is a need for a specific photoperiod, lights are left on for 24 hours. Growth is rapid in the system. A crop of leafy vegetables like spinach or soft leaved lettuce is ready for harvest in about four weeks. There is ample time to allow each student in each class to grow his or her own crop and perhaps time for some special individual projects at the end of the year. We usually celebrate the harvest with a pizza and salad party made from the classes own vegetables, of course. While in use the system can be used to visually demonstrate many important scientific principles from a variety of disciplines such as, animal and plant physiology, microbiology, and, of course, ecology.

The construction details are as follows. The hydroponic tubes are made from four inch diameter, thin walled drainage pipe. Each tube is five feet long and has circular holes 1-1/2 inches in diameter, cut every six inches with a keyhole saw. Jiffy 7 pots fit snugly into these holes. The tubes are filled with lightweight lava rock which provide excellent surface area for root support. Plastic pipe caps are glued to each end of the growing tubes . Inlet holes are drilled 1/4 inch from the bottom of each cap and tee shaped fittings are cemented into each hole.One half inch flexible tubing connects each tube to a submersible sump pump at the bottom of the aquarium. Overflow drainage holes are drilled 1/2 inch from the top edge of each cap. One inch diameter tees are cemented here and connected by plastic tubing. This returns any overflow to the tank.

A one-hour constant cycle timer activates the pump for approximately one minute, every half hour. When the timer goes off, the remaining solution will drain back through the pump through the fill line. A 24hour timer should turn the lights on and off at intervals that are appropriate for the plants being grown.

A thirty gallon aquarium or reservoir should be sufficient for this project. If you have a commercial plant growing rack, a pair of discarded aluminum crutches make a fine superstructure for light support.

Materials and Approximate Cost:

  • 25 feet of thin walled plastic drainage pipe ($20)
  • 10 feet of 1(one) inch diameter flexible plastic tubing ($10)
  • 10 feet of 1/2-inch diameter flexible plastic tubing ($6)
  • 6 plastic tees 1 inch diameter ($6)
  • 6 plastic tees 1/2 inch diameter ($5)
  • 2 tubes GOOP cement ($8)
  • 1 submersible recirculating pump ($80)
  • 8 boxes of lava rock ($40)
  • 1(one) 24hour on/off appliance timer ($7)
  • 1(one) 1hour constant cycling timer ($60)
  • Total cost = $242

Finally, included here is a drawing of the apparatus as well as an ecology exam using the hydroponic system as its focus.


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