A garden of fish

Photo by Madelayne Hajek
Photo by Madelayne Hajek

One of the main benefits of Concordia University’s Sir George Williams campus is its prime location in downtown Montreal. While the urban setting and fast-paced lifestyle of the city centre can be alluring to young university students, there is no denying that the carbon monoxide from street traffic can be hard on the lungs.

Above the urban chaos, on the 13th floor of the Hall building, is a space where students can breathe easy, drink tea and meditate alongside plants and fish. While it may be difficult to find on your first visit to the rooftop, the Concordia Greenhouse offers more than just a tranquil space to recharge. Part of Sustainable Concordia, the Greenhouse Project includes various projects pertaining to community building, urban sustainability, and food security such as the aquaponic system.

Since January 2010, coordinators Stefanie Dimitrovas and Jonathan Douaire have spent countless hours building, maintaining and nurturing their aquaponic system, a combination of hydroponics and aquaculture, also known as fish farming. Set up like an ecosystem with various forms of plants and animal protein, the aquaponic system has no need for soil. The plants are placed in bins filled with expanded clay and mounted on an aquarium filled with fish – definitely not your typical garden.

The life and growth of the system depends on the chemical relationship between three elements: plants, fish, and bacteria. Fish waste, which is mostly ammonia, at a high level can be harmful and toxic to the fish, but can often be used as fertilizer for plants. An aquaponic system is able to filter through the fish waste by nitrifying the bacteria, converting the ammonia into nitrite, and then into nitrate.

Nitrate is a great source for fertilizers because it is a biodegradable and soluble substance. While the fish provide a great resource for the plants, they in return clean the water for the fish with the excess nitrogen.

The key to the aquaponic system is the expanded clay, a neutral soilless medium that does not clog or rot. It contains a diversity of microbes, aiding in the system’s chemical filtration process.

“They are the ones converting the ammonia first into nitrite, and then nitrate,” says Dimitrovas. “It sort of oxidizes the nitrogen in a way to make it more available for the plants to take out.”

Fish is the preferable choice for urban aquaculture systems. Because of their tolerance for crowding and murky water, Dimitrovas and Douaire use goldfish. There are currently 24 fish in the tank, a population that depends on the volume ratio between the grow bed and the fish tank.

In order to keep a suited balance for such a system that will ensure enough filtration and benefit the plants, fish and microorganisms, the respected ratio should be one to two liters of grow bed to one liter of water in the fish tank. Once the system has ‘matured,’ the number animal of protein can be decreased.

While the number of fish is stable at the moment, Dimitrovas admits there have been three to four deaths over this past summer. According to their veterinarian, this lapse in the system was related to the lack of nutrients in their homemade fish food. They now feed their goldfish a combination of commercial food and their homemade concoction consisting of ingredients such as gelatin, greens, soy flour, multivitamins, cumin, carrots, seaweed and other fish like sardines.

Though the fish should be bigger in such a system of almost three years in age, the plants are growing quite well nonetheless. Dimitrovas and Douaire have experimented with various aquatic plants such as duckweed, arrowhead, lotus and milfoil. Over time, the system has matured enough to grow cucumbers, green peppers, and to Dimitrovas’ surprise, a papaya tree.

“We read that [papaya trees] don’t like too much moisture and they don’t like their roots sitting in water,” says Dimitrovas. “But it seems to be doing quite well and it’s been sitting here for months.”

Every week, Dimitrovas and Douaire test the water for nitrite, nitrate, ammonia, and pH levels. They keep a log and monitor the natural changes that occur and the necessary alterations that take place.

Keeping a log has allowed them to experiment, learn from their mistakes, study the limitations of such a system, and most importantly, and share their findings with students.

Although the project has been quite successful during the past few months, Dimitrovas and Douaire hope to expand and improve their aquaponic system. Their main goal is to develop a fish food recipe that will substitute ocean-fish animals with other sources of protein such as insects and earthworms; a protein source that that can take advantage of all of the organic waste produced in an urban environment.

“Aquaponic systems have the potential for urban agricultural uses because they’re compact and you can produce animal protein and vegetables,” says Dimitrovas. “Also, if you’re in a situation that you don’t have a lot of water, the water in here recirculates. So you could be watering your plants quite well, and you can really reduce the amount of evaporation if you’re in a dry area.”

In order to keep the project alive, Dimitrovas applied for grants from the Concordia Council on Student Life, and has agreed upon a trade with the Greenhouse. In exchange for being part of the overall Greenhouse budget, Dimitrovas and Douaire are growing seedlings to add to the plant sale and are giving workshops on the aquaponic system. They have currently set a date for their first workshop on November 7 at 4 p.m.


The Concordia Greenhouse is located on 1455 de Maisonneuve Blvd. W.





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