Aquaponics is the combination of fish farming and the growing of crops, such as herbs and vegetables.
It could potentially be the solution to food scarcity and could generate income for new farmers in South Africa.
Crops are grown the same in both hydroponic and aquaponic systems, as the roots come in contact with wastewater. The wastewater comes from tanks where freshwater fish are grown, and after the plant roots absorb the nutrients and filter it, the water gets fed back into the fish tanks.
Aquaponics Techniques
The following are general aquaponic techniques:
Deepwater raft aquaponics
In this system, crops are planted in a polystyrene raft in a relatively deep, 30 - 40 cm, waterbed. The advantage of this system is the consistency of the water temperature and pH, but a disadvantage would be that an extra biological filter is needed for the breakdown of ammonia.
Closed loop aquaponics
This system is also known as the ‘growing power model’. The aquaponic system uses fixed mediums like grit or clay beads. Crops are planted in the fixed medium in a container that gets overflowed with water from aquaculture tanks. This technique works best for creeper plants like strawberries, tomatoes and granadillas.
Reciprocal aquaponics
Fixed mediums such as grit and clay beads are used in a container that floods around the clock and gets drained when a certain water level is reached.
Drainage is important to prevent plant roots from being permanently underwater. This also prevents rotting. Water drainage goes through a row of drains, a clock siphon outlet, which drains the water in intervals.
This aquaponics technique is known as ‘flood and drain’ or ‘ebb and drain’ aquaponics. It is the ideal system for beginner farmers as it is easier to manage, and a large amount of crops can be produced. It also works well for plants that need more support, such as tomatoes, cucumbers and pumpkins.
Other aquaponics systems
The vertical system is made up of vertical plastic pipes that get fed water from above through rivulets.
Crops get planted in the openings of the pipes. The film nutrients technique has channels and horizontal PVC plastic pipes, like ‘gutters’, with openings for the containers. The water is then led horizontally to the containers that hang in the ‘gutters’. Plastic 200-litre drums get cut in half and filled with either grit or water, on which polystyrene rafts can float.
Aquaponics for New Farmers
The application possibilities for aquaponics technology are vast. It can be done on different scales, which would cater to different needs, from family-scale production for new farmers to a commercial level. Aquaponics can be done on a small scale, like in a backyard to grow fresh produce to feed a household.
Carp, tilapia or catfish can be used in a 500-litre fish tank. The reciprocal aquaponics technique or medium-growth beds are recommended for new farmers. Aquaponics technology is extremely suitable for new farmers for various reasons: It can be done on a small scale and can be expanded later.
It is not really labour-intensive. It can be set up with relatively inexpensive material. Fertile soil or large amounts of water are not prerequisites. Medium-scale aquaponics is suitable for the provision of fresh produce for a community, such as a school, retirement home, restaurant or hotel.
Aquaponics can be done on a commercial scale as a single entity and division of farming. The relationship between the amount of fish and plants will depend on the quality of the fish feed, the fish species and the type of variety of plant used. Plants that grow higher and fruit-bearing plants need more dissolved nutrients.
You’ll need technical knowledge before you start any form of aquaponics farming. It is thus recommended that new farmers get practical training before they start.
The Cost of Aquaponics Systems
Every aquaponics system has its advantages and disadvantages. The cost of aquaponics systems will depend on the size of the system, its design and the type of material used. It can vary between R1 000 to millions of Rands for big commercial systems.Market for Aquaponics Products
It might sound like a cliché, but the saying ‘the market is everything’ rings true in farming, it is the driving force behind all agricultural systems. Learn about the market by doing extensive market research before you start farming.
Speak to potential clients and find out what their specific needs are. Find out what types of plant varieties, or types of fish, and their needs, for example, what quantity you need and which time of year works best for growth. If possible, set up marketing contracts with clients.
It is also advisable to have a variety of products instead of a single product line, for example, a range of lettuce varieties and herb varieties. Focus on high-quality plant varieties like fresh herbs, berries and chillies; these products have larger profit margins.
The fish species that are used in aquaponics will depend on what type of species you are allowed to have in your environment. Find out from your provincial conservation department which species are most used in aquaponic farming in South Africa. It will most likely include bream, catfish, carp and ornamental fish.