Growing fruit and vegetables in the city is an increasingly important part of the food system. Localised food growing makes sense, particularly as rising food costs and an increase in extreme weather events threaten the current method of transporting food grown far away to our urban centres. Urban agriculture is one way to reduce food transportation and related carbon emissions, but traditional farming requires a lot of space, water and fertilizers. Growing food in the city requires some measure of ingenuity.
Aquaponics (a fusion of aquaculture and hydroponics) is a method of growing fish and vegetables sustainably by replicating the closed-loop nutrient cycle found in nature. Within an aquaponic system, fish and plants form a symbiotic living arrangement. Water from the pond is flushed through the soil-less plant beds where the plants filter the ammonia out of the water. Anyone who has had a pet fish will know that toxic build-up of ammonia in a fish tank is toxic for its fishy inhabitants. Given that ammonia is a complete fertilizer for plants, an aquaponic system is a water efficient way to feed plants and supply fish with plenty of fresh water.
Aquaponics is perfect for Australian conditions because it uses only 10 per cent of the water needed to grow vegetables in soil. It also requires only minimal inputs such as fingerlings (baby fish), fish food and a small amount of electricity to power a water pump, with any waste produced becoming an input for the system. There are ways to reduce these inputs further such as using solar panels as an electricity source and growing vegetarian fish species such as silver perch. You can even grow food such as duckweed for the fish yourself.
If the fish food is sustainably sourced, aquaponics could also help reduce pressure on wild fish stocks, already under great strain, as well as reliance on unsustainable fish farming.
You can find plenty of aquaponics advice online and there are many sites with open-source plans for DIY systems and forums for ongoing support. Not all websites offer sound advice though, so it pays to be selective. The number one rule is to be adaptable with your approach. There is no one right way to do aquaponics, every system will have unique quirks and styles.
While accessible, aquaponics is not for the casual gardener. It doesn’t take an engineer to build a small backyard system, or a horticulturalist/aquaculturalist to run one, but it does require daily attention, persistence and patience.
Aquaponics is perfect for a resourceful person with plenty of gumption. Keeping your plants and fish healthy, and the technical components working requires time, but with considered design and carefully selected species, the right set-up can grow a fingerling into dinner in less than a year. And if the idea of eating the fish doesn’t appeal, you could opt for goldfish as pets instead.
Robbie Kershaw has been working with aquaponics for five years, but his love of fish is lifelong: “I have kept fish all my life,” he says, “It is my passion, and I’m a keen gardener, so it seemed like a natural progression.”
Robbie has one commercial and one DIY system on his 400-square-metre property; the prettier of the two in the front yard, where it attracts much interest from passers by, and the less aesthetically pleasing system is out the back. The system has about 100 rainbow and brook trout on the go but he sees the fish as secondary to the vegetables, which provide a year-round supply for the family and the neighbourhood.
ROBBIE’S TIPS FOR AQUAPONICS AT HOME:
- A budget of $500 should cover the cost of materials and fish stock.
– A good pump is crucial as circulation is the key to maintaining a healthy ecosystem. A pump costs around $100.
– Make sure the plant bed beads are non-concrete and non-porous, to avoid contaminating the water.
– The ongoing costs of fish food and power to the pump are offset by low water use and trout dinners.
– Aquaponics only requires low energy input, but solar power is an option to reduce related emissions of the system. However, it is crucial that the pump runs 24-hours a day to avoid killing the pH-sensitive fish. Robbie advises beginners start off with a mains-powered electric pump.