Aquaponics has long been hailed as a potential resolution to food scarcity as it does not require as much land as traditional farming and can be done in an urban setting. Neale Strauch, the founder of Urban Aquaponics, gives us some insight into the industry.
Comparing aquaponics to traditional farming, says Strauch, requires a “plant to plant” approach. He explains that for every hectare that traditional farmers work, they produce around 20 000 plants, potentially up to 40 000 even.
“If you would do one hectare of aquaponics, you do 430 000 plants. So that’s the starting point, where you have 20 000 plants on a hectare versus 400 000 plants on a hectare.
“Now when you look at the cost, the only way to equate the costs is to say ‘what size of ground, [how many] tractors, and [how many] ploughs will the farmer need to plant 400 000 plants?’. Aquaponics comes in at less than half that price, initial investment price.”
He says, however, most aquaponics farmers do not farm up to 400 000 plants, the comparison is simply to underline how much cheaper it is to farm aquaponically. “But, if [we are talking] about startup costs, it’s going to cost, [before breaking even], about R3 million.”
Strauch has been in aquaponics for the last 11 years. An engineer by trade, he fell in love with aquaponics because it is such a measured science. “I got involved in aquaponics and I built a little hobby system in my back garden.”
Strauch says he made many mistakes in his earlier years but the more he practised aquaponics, the more it grew on him, and the more he improved his system.
“Eight years ago, I started writing training modules to help people along the way so that they don’t have to make the same mistakes as I did. That expanded to where I had no more space in my garden in Centurion. I then acquired a piece of ground, which was actually for my other electronics business, but there was enough space.
“Today, we have a commercial-sized system where we plant 80 000 plants, purely aquaponically. We use rainbow trout as the fish of our choice.”
But what is aquaponics?
Aquaponics is the combination of hydroponics and aquaculture, says Strauch. He explains that aquaculture is the growing of fish, or farming with fish, and hydroponics is the growing of plants using water systems.
“So, [when] we combine the two, we utilise fish [that] produce ammonia, which is then changed by Mother Nature to nitrates. There’s a process that [includes] ammonia, nitrites and nitrates, which go to the plants.”
These chemicals contain the elements, or micronutrients, the plants need to grow. The plants absorb these micronutrients, allowing the plants to flourish.
Strauch adds that with aquaponics, there are three living organisms involved: the fish, the plants, but there are also the bacteria. The bacteria, he says, is what converts the ammonia into the nitrates the plants absorb.
Which fish types are ideal?
There are three types of fish South African aquaponics farmers use, says Strauch. These are tilapia, rainbow trout and catfish.
Tilapia is common because it is a warm water fish, he explains. “Because our waters here are reasonably warm, that’s an easier fish to utilise. You don’t have to worry too much about the water except in the winter. You have to make sure your water remains at a certain temperature.”
Rainbow trout, he says, are cold water fish and they are more difficult to keep. “I always advise, ‘please first use the easier fish and then you can go to the trout’. The advantage is the price, of course, and they feed right through the winter, so you’ve got nutrients throughout the winter.“
The final fish species, catfish, are the easiest to keep. “They are air breathers. They don’t need a lot of oxygen in the water, but there is not much sale value in the catfish.”
The biggest deciding factor on the type of fish you farm with, is your location, says Strauch. He adds that the weather in your climate determines which fish will survive there and thus power your aquaponics operation. “If you’ve got warmer weather, you get the warm water species. If you’re colder weather, for instance, like in Mpumalanga, then you’d use the rainbow trout. Generally, what most people use is the species of tilapia.”
He says that temperature regulation is a possibility as well, but it ends up becoming an extremely expensive exercise that requires a lot of electricity.
“Unfortunately, with our power situation in the country [being] on and off, you have to spend more money. You can have heating systems and then like me, a cooling system. [I use the air] to cool the water, so it’s just the flow of the water that enables it to cool. Really, the ideal is to find the natural way of doing it, or else you have to spend. Your investment gets larger and larger because then you need a generator. Fish can’t survive without oxygen and the water temperature has to remain reasonably constant.”
What are the ideal plant types?
Strauch divides the plant types into three categories; leafy greens, fruiting plants, and rooting plants.
Leafy greens include herbs like mint and basil, as well as plants like lettuce and celery, and spinach. Fruiting plants are plants like tomatoes and cucumber.
“Now rooted plants are anything that grows under the ground, like a potato and radish. And those are not suitable within the aquaponics world because we don’t use soil. We only use water and, in some circumstances, we use stone, so the rooting plants are not ideal.”
Strauch emphasises that what you choose to grow, is informed by your market more than anything else. Your market needs to guide your choice in plants.
“The real choice is really not what you can grow, but what you can sell. Tomatoes grow unbelievably well in a methodology of aquaponics. But you’re competing against the large farmers [who] can produce those tomatoes at very low cost.”
For people who want to grow at home, Strauch advises they diversify their crops. “If it’s a home system, then you can have a tomato plant, and a cucumber plant, and a few lettuces, and a few spinach.”
There are three ways of growing things with aquaponics: the ‘flood and drain’ method, the nutrient film technique (NFT), and the deep water culture method.
The flood and drain method, says Strauch, is more common amongst smaller producers or hobbyists, and is not used commercially. The method is a stone-based system.
“You have a box [with] gravel stone in it. And the water flows into it and fills the box or the holder. There’s [also] a valve that opens and the water rushes [in and out]. That’s about a 20-minute cycle, that’s ideal for fruiting plants because anything that forms a tree or a bush needs some place for the roots to hold onto. So, it almost simulates soil.”
The NFT method is a system that uses large pipes to transport the water. “The water flows through [the pipes] but there’s only a film of water. That’s why it’s called the nutrient film technique. The plants absorb the nutrients out of the water that’s flowing through the pipes. It’s more expensive to build and therefore not [often] used commercially. That’s where I started, so I still have quite a lot of those.”
Deep water culture, also known as the raft method or floating system, involves the plants floating on top of the water in “rafts”. The Food and Agricultural Organization of the United Nations defines it as “nutrient-rich water is circulated through long canals at a depth of about 20cm, with rafts, usually polystyrene, [floating] on top. Plants are supported within holes in the rafts by net pots. The plant roots hang down in the nutrient-rich, oxygenated water, where they absorb large amounts of oxygen and nutrients that contribute to rapid growth conditions.”
Strauch says this methodology works best for commercial farmers, as it is cheaper to build and as successful as any other methodology.
“I advise [smaller growers] to start with a deep-water culture because [that means] you’re already growing like a commercial entity and you’re learning the lessons early, instead of going that stone-based.”
Can you farm both fish and plants at the same time?
When starting out, advises Strauch, farmers need to decide if they want to do aquaculture or aquaponics. He says that attempting to do both aquaculture and aquaponics is unsustainable. The reason for this is that breeding fish whilst trying to grow plants requires different infrastructure.
“As soon as a person really wants to go into the aquaculture side, the science changes. You need larger filtration. You need all types of other stuff to make that work.”
He explains that aquaculture farmers need to monitor the breeding cycle of the fish, and there are many factors to consider.
“A lot of people would say ‘you have your fish, so you can sell your fish and your plants’. But your fish take a long time to grow. And they don’t just breed and breed, depending on the species. Breeding is a cycle completely on its own. But we do sell out fish as they grow to a certain size.”
When setting up an aquaponics operation, Strauch says farmers need to add a certain weight of fish to their operations. The amount of plants produced is dependent on the amount and size of fish in the operation.
“We don’t refer to the amount of fish. It’s really the amount of fish and their size. You need 200kg of fish to grow 12 000 plants. And you can scale it all the way down, but you can’t come down to five fish and then you think you’re going to do 100 plants. You need to get the equation [right].”
Strauch also says that fish live for very long, depending on their species. He says some can live up to four or five years.
“You just keep feeding them so you’ve got the free nutrients from the fish. And you can sell out some fish to buy fish feed for them, as long as you keep the biomass, [which is] the 100kg or the 200kg of fish you need to grow your plant safely.”
One of the biggest challenges in aquaponics is securing a market with big retailers, says Strauch. Smaller retailers cannot offer the same consistency as bigger ones, and larger retailers do not really believe in the safety of their produce.
“We can’t spray any insecticides or pesticides or anything on our plants and it’s a simple reason: because it goes into the water and kills our fish. So we are forced not to do that, which makes our plants much healthier. The major challenge is really to get accepted by retailers as a specific, healthy growing methodology. We’ve put a lot of effort into that, and we keep on putting a lot of effort into it. “
He also says that major retailers want producers to have a Global Gap certification, something out of reach of most smallholders. “The smaller guy is really going to struggle to get there, [because they] didn’t have R200 000 to throw at that certification. That’s quite a limiting factor for any of our growers, to be able to enter the market and have their produce selling on the shelves.”
Strauch urges new farmers to get training on aquaponics. He says that it may be costly, but it is worth it in the end.
“You might think you have to spend [unnecessary] money, but you’ll walk away with everybody else’s mistakes in your back pocket. So, you don’t only get the success story, you actually get the mistake story as well, so you don’t make the same mistakes.”
For Strauch, the joy of watching his plants grow and feeding his fish is the most rewarding part of the job.
“You’ll go away for a weekend or so and you come back, and you see your plants have grown. It’s not waiting. It’s so fast because there’s so much nutrients in there. And that is really very rewarding.
“The fun bit is to feed the fish, because they are alive, they jump, they actually get so used to you approaching the dam, they know it’s feeding time. We feed four times a day and that’s a fun bit because you can see they’re healthy, they’re happy. So you’re doing something right.”
Sign up for Farmer’s Inside Track: Join our exclusive platform for new entrants into farming and agribusiness, with newsletters and podcasts.