Grow green around the gills with backyard aquaponics
Next to a warehouse in Northcote, there’s a long, white greenhouse. Inside, leafy greens and silver perch are growing together.
“Aquaponics is a form of gardening where you grow vegetables and fish in a symbiotic manner,” says Stephen Mushin, the scheme’s coordinator. “The fish wastes are converted into nutrients for the plants.
“It uses about one-hundredth of the water of a regular farm, so it’s especially suited to the dry Australian environment. And it’s suited to urban areas because of its space efficiency.”
That means it works well in backyards too: aquaponics is becoming increasingly popular with householders.
“The most exciting thing is that it’s a way of farming some protein at home,” Mr Mushin says.
“A large part of ecological footprint is in the food we buy and the way we dispose of food waste. By harvesting in your garden you can reduce packaging, water consumption and food miles. It puts food production in your face.”
If you buy a ready-made kit, it’ll cost you a few thousand dollars; if you build it yourself, it can set you back just a few hundred. Mr Mushin says well-designed systems require few ongoing inputs – they can run using water from your roof and need only a small amount of power for a pump.
On October 22 and 23, he’s teaching a short course on aquaponics at CERES, together with biologist Dr Wilson Lennard. Over the weekend, participants will construct a system combining a garden bed of 1 square metre, with a fish tank of 1 cubic metre.
Dr Lennard says rainbow trout is the best catch, because it tolerates a broad range of water temperatures. Depending on the species and conditions, the fish can grow from only a few grams up to about 750 grams in a year.
For the garden beds, he says, veggies will grow well in washed river gravel, which is cheap and widely available.
His most important advice, however, is to research well before plunging in. “You have to make sure you know what you’re doing. That’s mostly about looking after the fish – if you get the fish care right then the plants usually look after themselves.”
To keep the system in balance, you’ll need to test the water’s pH several times per week, keep an eye on its temperature and check nutrient and oxygen levels.
“People who have kept aquarium fish before usually have no problems because the principles are the same. If not, then I always suggest starting small to see how you go,” he says.
Dr Lennard specialises in commercial aquaponics, but he says that even on a small scale, it’s an economical option. “You need few fish and very little fish-food to produce enough nutrients for a lot of plants.”
Like normal gardening, he says, aquaponics will get you out and about. “It’s a good way to get back in touch with the planet – we all live such indoor lives nowadays. And it connects you even more to ecology, because it’s an ecosystem approach. It helps people understand water and nutrient flows, and how animals, plants and bacteria interact.”