Aqua-what? Perfectly poised to be important in the future of food for our growing population, aquaponic farming is extremely water-efficient, inherently organic and more productive by area than soil farming. Here are several healthy reasons why widespread adoption of aquaponics is a must, and also a few drawbacks to be aware of.
‘Aquaponics’ comes from the combination of aquaculture (fish-farming) and hydroponics (growing plants in a soil-less medium). Where hydroponics depends on a synthetic fertiliser produced from mined raw materials, aquaponics relies only on the nutritious pee and poo of fish. Some pretty helpful bacteria (the same ones that naturally ‘fix’ nitrogen in soil) convert the ammonia in fish waste into nitrates which the plants are able to take in through their roots, suspended in the water. These roots thereby filter the water which is then returned to the fish, resulting in a wonderfully symbiotic system. For the science nerds who want a bit more info, a decent summary of the process can be found here.
Nutrient-rich water flows from the fish tank to the plants, which suck up the nutrients, thereby cleaning the water before it returns to the fish. No soil, and very little water is lost. (Images: https://jerrysystem.blogspot.com and Dubai Aquaponics )
The theory is nothing new, popping up first in Aztec records and even being used in rice paddies in South East Asia since the 6th century. Modern scientific research only began in the 1970s, and after a bit of a slow start the aquaponics bug has spread to DIY farmers all over the world thanks largely to Youtube and other social media. There are now commercial operations in most countries and the combined hydroponics and aquaponics industry is expected to grow to be worth $2 billion in the next two years. As our future becomes more uncertain, more and more backyard hobbyists, NGOs and big commercial investors are taking an interest in it.
1. It is the most water-wise farming method
As far as water-efficient farming goes, nothing beats aquaponics. The water in an aquaponics system is continuously circulated between the fish tank and the root beds, so water is only lost through evaporation and transpiration from plant leaves (and usually the odd leak). A spinach or tomato grown in an aquaponics system uses 85% less water than being grown in soil. Hydroponics could attain the same efficiency, were it not for the necessary periodic ‘dumping’ and refilling of the water reservoir, which sets it one rung below aquaponics on the water efficiency ladder.
Vertical aquaponic farms are a novel way to grow on disused urban rooftops (Image: inhabitat.com)
2. It is extremely space-efficient
The only space competition between plants in an aquaponics system is really for light, meaning that plants can be grown much closer together than in soil.
This is because in soil, plant roots have to work at extracting nutrient molecules from the soil particles they are clinging to. Water, however, can carry a higher concentration of nutrients than soil, and these nutrients are freely dissolved in the water – all the roots have to do is slurp them up like a smoothie. The water is constantly being circulated, so there is never a shortage of nutrients for the roots to suck out of the passing water stream.
The use of pipes and towers go even further by making use of vertical space. As long as there is space, the sky is the limit. Think of disused rooftops, balconies, bare walls and abandoned warehouses – indeed growing productively within city limits will reduce demand for farmland, shorten transport distances for food and rebuild a healthy connection with our food sources.
3. Aquaponic veggies grow like weeds!
The fact that nutrients are easily available to the plant roots submerged in the water means that plants do grow faster than regular soil-based farming. In my own experience, kale and spinach grown in aquaponics reached double the size of those grown in soil at the same location. Heading lettuce can go from seedling to harvest in 30-35 days, compared to around 50 days in soil growing.
The Lebanese cucumber test(Image: Ecofilms.au)
Mature fish can harvested every few months too. While in a small system fish cannot be harvested often, in bigger systems the fish component can form a good chunk of the produce and profits if well managed. Tilapia are the most common fish used, while trout and carp work well in colder climates, and even fresh water crayfish do the job. Alternatively, treat your fish as your friends and let them live long and happy lives – they are in the end doing all the work for you anyway!
4. It is inherently organic
Adding any unnatural substances to an aquaponics system will affect the fine-tuned equilibrium at which the ecosystem functions. Add pesticide to your plants, and you will kill your fish. Add growth hormones to your fish food, and the plants will suffer accordingly.
Aquaponics systems are less susceptible to pest damage than soil growing at ground level: the plant growing area is generally raised off the ground, in pipes or in troughs, which has a tremendous effect on how many insects can make their way up there. Most aquaponics systems, especially in temperate climates, will be housed in greenhouses. Keeping these well contained almost excludes pests altogether.
While hydroponics systems are kept relatively sterile to avoid infections by mould and such, aquaponics systems are in essence robust and resilient ecosystems, strong enough in their own immune systems to resist similar threats.
Work done by Blue Soil in Vietnam and France is also using a bacteria-rich byproduct from aquaponics to help speed up the revival of soils degraded by monoculture and fertiliser overuse.
Waist-height NFT systems provide the perfect ease of care and harvesting (Image: EU Aquaponics Hub)
5. It is labour-friendly
Compared to bending down in a garden and the back-breaking shoveling of soil and compost, aquaponics systems can be ergonomically designed to be worker-friendly. Grow beds at waist-height mean no need to bend over when planting, pruning or harvesting. Methods of planting seeds, seedling transfers and harvesting can be tailor made for the least amount of back pain.
Consider too the ease of the ‘harvest your own’ vertical pipes, unplugged from the system and propped upright in the veggie aisle of your nearest supermarket. Keeping the roots on a plant keep it fresh for much longer too.
Harvest-your-own grow towers allow customers the novelty of picking their own food, and also drastically reduce labour costs. (Image: Ichthys Aquaponics)
1. It is a labour of love
Anyone can start up their own system at home, from adding a growbed component to an existing fishtank, to everybody’s favourite beginner setup, the IBC tank. But as one increases the size of the system, the water chemistry management gets a bit more finicky, at least in the early stages before the system settles into a resilient ecosystem. In a well managed system, measurements of water parameters are done bi-daily and fish are fed 2-3 times a day.
Automation can help, but unlike hydroponics, an aquaponics systems should be treated as a living breathing organism. Important clues about system health can be gained from observing fish behaviour and close inspection of the plant leaves. There is a lot to learn from treating the system on the whole as a friend, learning to ‘listen’ to it and spending time with the plants and fish as you would in your favourite forest clearing
2. Ocean-derived fish feed is unsustainable
Because your fish food is essentially the only input into the system, that means that all the macro and micro elements that we would obtain from our vegetables need to be present in the food itself. Aquaculture-grade feed should be used to ensure the right combination of amino acids for your fish, as well as containing the cocktail of micro elements that your plants need.
This then poses a bigger problem – most fish feed, and indeed a lot of pet food, is obtained from ocean-fishing operations. A lot of soy is often present too, so one must consider the impact of animal feed on deforestation in the Amazon for example.
Eating farmed fish is often seen as being more ocean-friendly, which is only the case where a sustainable feed is used. Thankfully, sustainable insect-derived feed is becoming more and more available. Prolific producers like the black soldier fly that eats all manner of animal and plant waste, hold a lot of potential. They themselves provide the solution for the global protein problem, at 45% protein compared to 18% for chicken and around 25% for fish (more musings on this topic coming to L&S soon).
Black soldier fly larvae – the future of animal (and human?) feed. (Image: scmp.com)
3. Start up costs
Chuck a bit of manure and straw into your soil and essentially you have organic farm. But aquaponics does require a bit of start up capital – the biggest costs being on water and oxygen pumps, fish tanks and, if you are going the whole way, solar panels and batteries to power the pumps. The plus is that the system will last for a long time, so those costs can be recovered, and the lower labour cost over time can justify this too.
Fish feed is also a regular cost, and many small scale commercial operations have failed because of being unable to sustain this cost purely on the sale of vegetables to a market not yet willing to pay a premium for high-quality organic produce. For smaller operations, black soldier fly or earthworm offer a free protein source for fish.
3. Microplastics
An aquaponics system is essentially made of plastic pipes and tanks. While a lot of the higher grade tanks are food-safe, most systems still make use of regular PVC piping and fittings. The jury is still out as to how much plastic can dissolve in the water and how long it takes before that starts to happen. However, the same is true for a lot of our plumbing in our homes anyway, and it is quite likely that your home garden has dissolved micropoplastics in the soil. The jury is still out as to whether microplastics pass through our bodies without harming us too.
Food-safe grow pipes and tanks are only available to those with deep pockets or well-funded commercial programs, but the price should start decreasing with demand. Bamboo pipes are another alternative, though prone to leaks and mould
There we have it. Aquaponics brings sustainable and organic food closer to home. Importantly, the water efficiency of aquaponics simply cannot be ignored when climate change and the resulting desertification is already drying up farms across the globe. The fact that a system can run anywhere from the Sahara desert to the north pole, makes it something to consider for large scale commercial implementation and self-sufficient homes alike.
With dwindling land available, much of it with ‘sick’ soil, and the promise of 3 billion new mouths to feed by 2050, the “Aquaponically produced” label will soon be coming to a grocery aisle near you.
