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A new way to grow plants in water

Listed as one of the top gardening trends for 2013 in our January/ February 2013 issue (see page 136), aquaponics is being heralded as the most water-wise ways to grow plants. House and Leisure set out to discover why this gardening method is becoming so popular locally. We posed a few questions to Gina Gallinetti of MyAquaponics, South Africa’s leading aquaponics and hydroponics online store.

What is aquaponics?

Aquaponics is the farming of plants and fish in a recirculating system. It is a combination of aquaculture (growing fish) and hydroponics (growing plants without soil).

Fish and food waste accumulates naturally in a fish tank or pond. This leads to high levels of ammonia, which if not kept in check, becomes toxic to the fish. Plants, on the other hand, require nitrate and water for healthy growth.

The trick therefore is to convert the toxic ammonia into nitrates and to clean the water at the same time by introducing a natural bio-filter.

Why do you think this is a good alternative for growing plants?

  • Aquaponics uses 90% less water than soil-based gardening.
  • It is 500% more productive on a per square metre basis, compared to soil-based gardening. It allows you to plant more densely than conventional gardening and the plants grow up to three times faster.
  • You can grow your own mercury-free fish and enjoy a delicious meal.
  • It allows you to grow fish, vegetables, herbs and fruit at the same time.
  • It is totally organic – no chemicals, hormones, antibiotics or additives required.
  • You get to enjoy double the benefits of hydroponics.
  • Fish feed is a lot cheaper than commercial hydroponic nutrients. Grow the right fish, and you don’t even need to buy special fish feed.
  • You can run the system for years with very little maintenance.

Can you also grow edible plants via this method and are they safe to eat?

Yes, 100% safe. In fact, man has been growing plants this way for thousands of years. Here is some history on how aquaponics started:

Long before the term ‘aquaponics’ was coined, the Aztec Indians raised plants on rafts on the surface of a lake in approximately 1 000 AD.

Before the Aztec people had built a great empire in Central America, they were a nomadic tribe in what is today central Mexico. They settled near the marshy shores of Lake Tenochtitlan. Since this fresh water lake was surrounded by marshes and rising hills, the Aztecs were faced with the problem of trying to find a place to grow food. They solved this problem by constructing large rafts out of reeds and rushes they found near the lake. They floated these rafts in the water and covered them with soil that they dredged up from the bottom of the shallow lake. They then planted their vegetable crops on these floating islands that they called ‘chinampas’. When the plants matured, their roots grew through the soil and dangled in the water.

In modern times, aquaponics emerged from the aquaculture industry as fish farmers were exploring methods of raising fish while trying to decrease the dependence on land, water and resources.

Traditionally, aquaculture was done in large ponds but, in the past 35 years, much research and progress has been made in recirculating aquaculture systems (RAS). The great benefit of recirculating systems is that you can grow up to 0.34 kg of fish per 3.78 litres of water. This means that large quantities of fish can be grown in an Aquaponic Food Production system using a fraction of the space and water traditionally dedicated to aquaculture.

The disadvantage of highly concentrated populations of fish is the large volume of wastewater that accumulates daily. Early on in the research of RAS, experiments were done to determine the efficiency of aquatic plants in consuming the nutrients in this wastewater, therefore helping to purify the water for the fish in the system. As research continued, terrestrial plants were tested and proven to be an effective means of water purification for aquaculture and this nutrient rich water a nearly ideal hydroponic solution for growing plants.

What sorts of fish are used for these systems?

You can basically grow any type of fish in your aquaponics system. It all depends what you want to achieve, and where you are located geographically.

If you want a good eating fish, then we recommend the Red Breast Tilapia (Tilapia Rendalli). However, this is a warm water fish and the water has to be maintained at a temperature above 28ºC for optimum results. You may also need to contact your local authorities (departments of agriculture or fisheries) to confirm that you are allowed to keep a particular species of fish.

In South Africa, you may also want to try catfish (barbel), carp, trout and Koi.

The rule of thumb is that you can have up to 50kg of fish per cubic metre of water. In our aquaponic DIY system, you will be able to have up to 40kgs of fish at any one time.

Are these tanks suitable for people living in apartments and smaller homes too?

Yes, you can use many different size tanks for aquaponics. Be it a small counter top system in your kitchen or a larger 100 litre tank on your patio, aquaponics is very versatile. (Read more about how to build your own aquaponics tank at home here.)

Do these systems require a lot of maintenance once they have been installed?

Daily maintenance of an aquaponics system requires water quality testing as needed, filling of feeders, cleaning of piping and equipment, visual verification that all systems are in order, and finally record keeping to document any changes and note yields. Stocking, sampling and harvesting of tanks and planter boxes are required periodically.

Seeing that our Trends issue is currently on shelf, what other gardening trends do you see cropping up at the moment?

For me, it’s ‘keep it simple’ in the garden, ‘but find a better way of doing things.’

I see a lot of alternative gardening coming, like aquaponics, hydroponics, bubbleponics, aeroponics and vertical gardening. I think it’s a great way to get the younger generations involved; I mean, what kid doesn’t like to look at fish? I see a lot of DIYing in these alternative gardening methods and even more upcycling for gardening in general. For example, we have many clients upcycling their existing Koi ponds into aquaponics systems (keeping their Koi fish and growing plants at the same time).

For more information visit myaquaponics.co.za or email info@myaquaponics.co.za.