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Oh yes! You can rear fish on your balcony

By George Mbakaya | May 19th 2018 at 00:18:23 GMT +0300

Fish farm

Sometime last year, I wrote a piece on soil less farming and it elicited impressive reaction. Many farmers wanted to know how to get started while others wanted to know sources of soil less media.

But one farmer from India shared with me her experience about growing fish and plants together — aquaponics farming. This is an agribusiness venture you can embrace if you have limited space.

Getting started

The concept begins with fish poo and pee, both of which contain lots of ammonia. Worms that live in rooting substrates break the solids down then bacteria convert the ammonia into nitrate, which acts as fertiliser.

As the plants suck up these nutrients, they purify the water, which benefits the fish. By which point the fish will once again need the ‘toilet’, and so on. It’s a virtuous circle.  

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As a result, no fertilisers are required, the water is continually recycled rather than being lost in the soil and no pesticides or herbicides are used.

The outcome is locally produced fish and plants that will give the customer the peace of mind that the food they are eating is healthy, free from pesticides and herbicides.

What’s more, aquaponics offers one more magic element — flexibility of design. This means fish and plants can be produced nearly anywhere — warehouses, roof tops, basements and balconies.

Fish are raised in tanks, troughs or outdoor ponds, where the produce excrement. The water with the waste from the tank flows to a hydroponics tray where plants grow in the water without soil. The waste is toxic to the fish but is a rich fertiliser for the plants.

As the plants absorb the nutrients, the water is purified for the fish. The clean water can then be recycled to the fish tank.

What to grow

Any leafy greens such as lettuce, kale, Swiss chard and arugula are the easiest to cultivate, he said. You can also grow herbs such as basil, mint and chives. Other crops include cucumbers, shallots, snow peas, eggplant, tomatoes, cabbage, cauliflower, peppers, beans, squash, red onions and even potatoes. The fish container can be made out of fiberglass, concrete or plastic.

Type of fish

In an aquaponics, there is no right or wrong type of fish. However, there are a few factors you should consider when choosing fish for your aquaponics system.

First, know what you want to achieve with the system, the prevailing climate in your city, and the supplies which are at your disposal.

If you do not eat fish you can probably use goldfish which can then be sold for some cash. You can add catfish or Tilapia if you like eating fish.


With aquaponics, year round growing is possible (for indoor systems), and the system is even more water efficient than hydroponics, producing two products using the same water.

Fish food is the only major input required, and it’s easier to use bio-controls against pests compared to soil-based agriculture.

Environmentally friendly

Most food production is dependent on oil and thus vulnerable to volatile prices, and many inject toxicity into our environment and compromise long-term sustainability. The other advantage is that during the warm season the plants get a lot of warm water through the system’s continuous flood and flow system.

Ultimately, this ensures they are always hydrated and are getting the nutrients they need to flourish.

The aquaponics system happens to be the most efficient and eco-friendly way to grow plants and raise fish in a small space. However, it is important that you setup the system correctly with the right materials so that things continue to run smoothly providing a healthy environment to the fish and vegetables.

[The writer is an expert on sustainable agriculture and agricultural solutions [email protected]]  

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