A research team at Vancouver Island University's School of Fisheries and Aquaculture has developed an innovative aquaponic system where fish are used to fertilize vegetables and vice versa. (Vancouver Island University)First came the home-based vegetable gardens.

Next, a few agrarian-minded people began toying with backyard chicken coops.

And now, if an innovative project at Vancouver Island University in Nanaimo, B.C., gains enough steam, the next frontier in backyard farming might actually be fish.

A research team led by technician Anne McCarthy has become a pioneer in the field of aquaponics — the combination of aquaculture and hydroponics — to create self-contained sustainable ecosystems capable of food production.

The prototype at the school's fisheries and aquaculture department uses tilapia and produces no waste — only fresh vegetables, fish that's fit for human consumption and filtered water.

Tilapia live in a bathtub-sized tank full of water. The fish waste is collected and used as fertilizer for the plants. In return, the plants filter the water, which is then pumped back into the fish tank where the cycle begins again. Similar systems have been around since the 1970s but are only now beginning to draw attention from hobbyists and sustainable-living enthusiasts.

"Basically, you use fish as your nutrient source to grow vegetables," McCarthy says. "You can, of course, eat the fish, too, but some people are only looking for a better way of growing vegetables at home."

The school's system is the size of a small room, but it could be scaled up or down to work in various settings — from suburban backyards to industrial fish farms.

The system works by using food waste produced by the fish to feed vegetables, which in turn filter the water for the fish. (Vancouver Island University)

"It could be really useful in fish farms, because typically, we have to put them in the ocean where we don't have control over the environment," McCarthy says.

"The great thing about aquaponics is that you can take it on to dry land and control all of the variables."

The commercial fish farm industry has come under fire for the level of toxins such as mercury in the fish, and the fact that they're farmed in open-net pens — devices that some conservationists blame for disease in native wild stocks.

The school's system is better than all that because there are no dangerous chemical by-products, something that can't be said of conventional hydroponic vegetable gardens, McCarthy says.

The school uses tilapia because it grows quickly, is a voracious eater and is extremely hardy. But researchers have also had some success experimenting with rainbow trout, a species native to Canada that thrives in cold climates.

The system isn't commercially available yet, but it's simple to duplicate and scalable. One student's early model essentially consisted of goldfish in an aquarium, along the top of which she grew basil.

"It's so simple," she says. "If you can keep a goldfish alive, you can do this."