Aquaponics is a combination of aquaculture – raising and farming fish – and hydroponics – growing plants in water. When combined into a single system, the fish waste provides rich nutrients for the plants and the plants provide a natural filter for the water that the fish live in. The third element consists of earthworms which help to break down excess waste and assist in mineralising the solid build up in the growing beds. Bacteria are also responsible for converting the ammonia from the fish waste to nitrites which provide food for the plants.
This ingenious system doesn’t require a lot of space and uses less water and other resources than soil-based agriculture. Aquaponics can work as a small-scale set-up for a single household, or it can be a huge commercial set up. It’s fairly low-tech, isn’t labour intensive and is relatively inexpensive to set up. A small system can be set up for less than $500 and provide enough protein and vegetables for a family all year round. The system can easily be adapted for both urban and rural areas and it can be run ‘off grid’ with the use of solar powered pumps.
Local organization, Hands of Hope in partnership with TEAM – The Evangelical Alliance Mission and the American-based organisation Hear the Cry, are in the process of setting up an Aquaponics project near Epworth called Habitation of Hope. The first phase of the project started in April and it is hoped that the project will produce enough fish and vegetables for their own needs as well as supplying nutritious, organically grown produce for the Epworth community.
Hands of Hope support 18 orphanages and feed up to 1,700 children across the country every day. Apart from providing healthy and affordable food, the project also provides training for the older children so that they become self-supporting adults when they are ready to leave the orphanage. The idea is that once the teenagers are familiar with the system, they can train others to be self-reliant and food secure.
Harare News spoke to Jephat Chifamba, from Hands of Hope and Steve Love from TEAM who were happy to show off their ‘work in progress’. Their project consists of six separate units, each comprised of a tank for the fish, gravel grow beds and cement tanks called ‘deep wells’. The water from the fish tanks is pumped into the grow beds – a plastic tank holding the growing medium – (in this case ¾ inch gravel stones, which sustain the plants) and then some of the water is returned to the tanks while some goes into the deep wells. The deep wells have perforated kaylite floats which support more plants. The system is quite efficient with an estimated loss of 15 to 20% of the water, mainly due to evaporation.
It is important that the water is constantly tested to make sure it has the correct pH levels, level of nitrates and other minerals. The temperature of the water also needs to be controlled and monitored. The fish tend to prefer higher temperatures, while the vegetables prefer lower temperatures and controlled humidity levels. These variables can be easily controlled with simple low-tech greenhouse and shade cloth structures. If the fish tanks are partially submerged into the ground this also helps to maintain constant temperatures.
The fish used in this project are Nile Tilapia which are tasty and versatile and quickly grow to reach harvest size. Unlike fish from other sources like Lake Chivero, these fish are free of toxins. The vegetables are organically grown without the use of artificial fertilisers or pesticides meaning they are much more nutritious and tasty.
There are future plans to set-up a bee keeping project so that the bees can help pollinate the crops as well as providing honey for the community.
For more information contact Steve Love: [email protected].
Image: Partially submerged fish tanks – part of the Hands of Hope aquaponics project in Epworth.