Articles and Information

"Students Having Fun While Using Aquaponics
to Learn About Their Environment"

by Scott Jones

Reading about environmental problems in a book gives students a rough idea of the problems facing mankind. It also gives them headaches trying to visualize the obstacles and solutions to pollution and habitat destruction. Reading a book doesn’t give nearly the viewpoint that a student gets when they get their hands dirty and wet. Hands-on learning brings home the message that stays with a student for life.

Students at Northview Middle School (grades 6-8) in Norfolk, Virginia, a chartered environmental magnet school, have a special interest in the environment. They live at the mouth of the largest navigable bay in the United States, the Chesapeake, one of the most environmentally threatened bays in the world. The Bay drains pollution from five states and Washington DC and has gone from one of the most ecologically active regions on earth to one of the most threatened. Norfolk ends up on the receiving end of the wastes and excesses of one of the most heavily industrialized areas in the world. The students at Northview don’t just learn about their Bay from books, they visit it every chance they get. But trips out to the Bay are hard to arrange and harder to fund. So they have done the next best thing, they brought the Bay to the school! This spring the students set up two aquaponic systems, one for water clarity studies and one as an artificial wetland/bay study and a comparative 8 trough NFT system for acid rain studies.

The water clarity aquaponic system uses a glass 125 gallon aquarium for the "bay" (what better way to see the clarity of the water?).

A siphon connects the "bay" to the natural clarifier of the shallows, in this case a 29 gallon open well clarifier, where fish wastes, scales, students’ potato chips, etc. settle to the bottom.

The water then flows through the sand banks (rockwool flock in a separate 29 gallon reservoir) for removal of fines and initial biological filtration. A 500 g.p.h. pump moves the water up to the eight NFT troughs at the "head" of the system (it’s hard to make clouds to pump the water to the mountains when inside a classroom).

Eight PVC troughs form small streams flowing from the "sand bank" where 160 plants devour the nutrient wastes from the water before it flows over the eight small waterfalls, picking up oxygen on the way, and empties back into the "bay."

The ecological loop wouldn’t be complete without the plants contributing their part to the food chain. Leaf lettuce, herbs and other plants are harvested and fed to the fish swimming in the tank. Supplemental feed (commercial fish pellets) are also available for the hungry fish. For ease of use, Tilapia are raised in the tank. Tilapia may not be native to the waters of the Bay but they are the most widely grown fish in schools due to their hardiness and forgiving nature.

Wetlands are the most efficient of Mother Nature’s filtration systems. Bogs, swamps and marshes are teaming with life. The water in a bay or pond would soon choke on its own wastes were it not for the biological and mechanical filtration of the surrounding wetlands. Students LOVE going to the wetlands. Where else can they happily splash in mud (coated up to their ears), splash water on each other and still say that they are "working on their education?" But having muck-covered children wandering the halls of the school all day makes for a messy school, so Northside Middle School brought the wetlands into the classroom. They didn’t fill the wetlands with stinky bog soil; they filled it with clean rockwool flock and expanded pellets (Leca Stone). Now the students get to experience and experiment with wetlands all year ‘round and get to "play in the water" without becoming a "Creature from the Dark Lagoon." Even the educators enjoy dabbling in the clean flowing waters of the system after a hard day teaching.

The wetlands system consists of a 200 gallon poly tank, airlifts to move and oxygenate the water and a rockwool/lecastone filled 4x8x1 poly growbed set on blocks. The water flows continuously through the system, matching the constant slow filtration and replenishment of nutrients to the plants that Mother Nature uses. The 32 cubic feet of biofiltration media theoretically can successfully handle a 2,000 gallon tank and over 1,000 pounds of fish so, even if students overfeed the fish, there is never a danger of devastating system crashes.

For maximum safety, airlifts are used to pump the water. No electrical water pumps are used. This also allows the system to safely handle low water levels; airlifts simply stop pumping when the water level drops too low. Electrical water pumps would continue to pump ALL of the water from the tank should problems occur (making very unhappy fish) and then burn out when the water runs out. (See "Blowing Hot Air" by Scott Jones in the November ’98 issue of Aquaponic Journal for a more technical overview on airlifts).

Using airlifts for pumping also allows the system to remove fatty wastes with a foam fractionator when loadings get high. Foam fractionators collect dissolved wastes on the surfaces of the bubbles and remove the wastes from the system by producing foam that is easily skimmed off from the water column at the top of the airlift. While the poundage of fish in the system is low, it is plumbed to return the wastes to the system for breakdown by the plants in the growing bed. When the loading gets higher, the fractionator is plumbed to dump the foam into a bucket for disposal on the soil-based gardens outside the classroom windows.

During the fall semester the students will be growing regular garden plants in the growbed. In the spring they will be going out to the bay on field trips to collect just-emerging bay grasses to put into their system to convert it into a true Chesapeake Bay wetlands. Since Tilapia are adaptable to fairly high salt levels, the students will be able to match the salinity of the Bay in their system and provide the halophyte plants with their ideal environment.

Until the fingerling Tilapia reach a larger size and are producing more wastes, the plants are fed additional nutrients with foliar feedings.

Acid rain and pH studies are a fact of life in a school that specializes in environmental science. To get hands-on learning of plant responses to various levels of pH, the students use an NFT system that has eight separate trough/pump/reservoir modules. By varying the pH in each module by 0.5 pH they can see first-hand how field crops such as corn, lettuce, tomatoes and wheat adapt (or don’t adapt) to acidic and alkaline extremes. Up to 15 plants can be grown in each 5' trough and, since the plants are grown in individual rockwool cube/pots, the plants that don’t thrive can be switched to a different pH in a neighboring trough simply by lifting them up and dropping them "next door."

The students at Northview Middle School are learning first-hand about their environment and how they can mitigate the mistakes of the past. They’ve dipped their fingers in the future of hands-on learning and are absorbing the lessons of ecological science. Best of all, while they are gaining usable knowledge in the classroom, they are doing what students everywhere like to do most: they are having FUN!

The systems mentioned in this article were designed for educational use by Hydro/Aquatic Technologies and assembled and operated by the students of Northview Middle School with help from Scott Jones.

About the Author: Scott Jones is the head of Research and Development at Hydro/Aquatic Technologies, Princess Anne, MD and a regular- featured writer for the Aquaponics Journal. He can be contacted by e-mail at aqua@hatech.com or phone at 410-957-2680