University of Vermont Students Design Aquaponics System; On Display in Aiken Center

By Anna Marchessault, Program Assistant
November 06, 2022

While aquaculture has been a focus of research and workforce development in coastal states for decades, the field is just beginning to gain traction in the Lake Champlain basin.

In the wake of COVID-19, Lake Champlain Sea Grant hired Aquaculture Specialist Theo Willis to introduce land-based aquaculture to the watershed to increase local food security and develop an aquaculture education program. Willis soon fostered multiple partnerships in the region, including with the University of Vermont Rubenstein School of Environment and Natural Resources (RSENR), to educate and engage students.

In the spring of 2022, Willis and Eric Roy, Associate Professor at RSENR, collaborated to build an aquaponics system in the Eco-Design Makerspace, located in the Aiken Center at the University of Vermont. Aquaponics is a food production system that couples aquaculture with hydroponics, using the nutrient rich fish waste to feed the plants. The Eco-Design Makerspace was formerly the Eco-Machine, a living laboratory that successfully treated 760,000 gallons of the building's wastewater over five years. The Eco-Design Makerspace is highlighted in campus tours and receives many visitors from students, prospective students, and community members.

Roy and his Ecological Design students transformed the space into a display of student projects that model elements of a circular economy and nutrient recovery, which both showcase using conventionally waste products in a new way. The Makerspace showcases student-designed microcosms, hydroponic growing systems, fungi cultivation and experimentation, and nature-based art. Displaying aquaponics was always an exciting prospect for Roy.

About ten students in Roy’s Advanced Ecological Design class participated in the building of the aquaponics system. The class was a mixture of Natural Resources students and Engineering students, each bringing their own expertise. Students from this class continue to be the main stewards of the system, collecting data about nutrient levels, temperature, pH, and chlorine so that the system maintains balance and efficient production of both fish and plants.

“We hope this system acts as an example to teach passers-by what aquaponics systems are,” shares Hailey Sanphy, an Advanced Ecological Design student who is monitoring the system. “We want to show that aquaponics systems are scientific, but they’re also accessible, efficient food sources!”

Aquaponics System Details

The aquaponics system at the Aiken Center consists of a series of tanks, each with a different purpose. The first tank is the biggest; this is where the nearly 150 tilapia fish live and feed. The water is then sent into a smaller tank called the clarifier, where the largest particles from the fish waste are strained out and removed. Here, plants like basil and kale can thrive above the filter media, growing deep roots.

The next—and maybe most important—tank is the biofilter. The same size as the clarifier, this tank is set up with small clay pebbles that are covered with beneficial bacteria that convert ammonia from the fish waste into nitrite and then nitrate, a usable nutrient for plants that, unlike ammonia and nitrite, is not toxic to the fish. The newly nitrified water is then pumped into the main plant bed. The bed takes about 20 minutes to fill up with water which allows the roots of the plants and the bacteria to soak in the nutrients before draining to bring oxygen back into the system.

Finally, the water is pumped through a traditional hydroponics system that uses a nutrient film technique (NFT) to feed the plants. The water eventually circulates back to the fish tank.

“The whole system is a tricky balance: everything has to be just right for the fish, bacteria, and plants to be happy,” explains Willis. “That’s why we have constant monitoring of variables. The students coded and assembled a monitoring system that sends updates right to their email. If something isn’t looking right, we can catch little problems early before they become big issues.”

In these aquaponics systems, Willis, Roy, and the students grow kale, greens, okra, and numerous herbs, and they hope to add other vegetables to the mix soon. They have a growing partnership with the Rally Cat’s Cupboard to donate the harvests. Rally Cat’s Cupboard is an on-campus food pantry focused on increasing food security at the University of Vermont.