We discussed hydroponics before, which is a method of growing plants without soil, using mineral nutrient solutions in a water solvent. My concern with traditional hydroponics has always been the expense of the nutrient solutions.
Today we look at aquaponics which is a system that combines hydroponics and conventional aquaculture (raising aquatic animals such as snails, fish, crayfish or prawns in tanks) in a symbiotic environment.
So what does this mean? “Symbiotic environment” big words. It basically means the shit of the animals will provide the nutrients for the plants to grow. In fact, I am going to take this a level up: a chicken coop on top of a fish tank/pond (tilapia) providing the nutrients to grow plants and herbs hydroponically all automated.
The chicken poop will feed the fish, the fish waste will feed the plants, and some of the plants will feed the chickens. All in one system that produces organic food in a small space. This can be built in a backyard.
First things first what is happening here? And is it safe?
The chicken and aquaponic system are common in some Asian countries. To understand the process, it goes like this: chicken manure produces planktons which provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish and whales.
This concept is not new, in their paper on integrated chicken-fish farming, Modadugu V. Gupta and Francisco Noble explains:
Chicken raising for meat (broilers) or eggs (layers) can be integrated with fish culture to reduce costs on fertilizers and feeds in fish culture and maximize benefits. Chicken can be raised over or adjacent to the ponds and the poultry excreta recycled to fertilize the fishponds. Raising chickens over the pond has certain advantages: it maximizes the use of space; saves labour in transporting manure to the ponds and the poultry house is more hygienic. No significant differences have been observed on the chickens’ growth or egg laying when they are raised over the ponds or on land. In case of the former, the pond embankment could still be utilized for raising vegetables.
So that takes the why of the chicken pen out of the equation. The rest is just basic aquaponics which Wikipedia explains as
“In an aquaponic system, water from an aquaculture system is fed to a hydroponic system where the by-products are broken down by nitrifying bacteria initially into nitrites and subsequently into nitrates that are utilized by the plants as nutrients. Then, the water is recirculated back to the aquaculture system.”
Here is a picture if that sounded too complicated for you.
Here is a simpler pic if you still don’t understand:
How it works
Aquaponics consists of two main parts, with the aquaculture part for raising aquatic animals and the hydroponics part for growing plants. Aquatic effluents, resulting from uneaten feed or raising animals like fish, accumulate in water due to the closed-system recirculation of most aquaculture systems. The effluent-rich water becomes toxic to the aquatic animal in high concentrations but this contains nutrients essential for plant growth.
Components of an aquaponic system include:
Rearing tank: the tanks for raising and feeding the fish;
Settling basin: a unit for catching uneaten food and detached biofilms, and for settling out fine particulates;
Biofilter: a place where the nitrification bacteria can grow and convert ammonia into nitrates, which are usable by the plants;
Hydroponics subsystem: the portion of the system where plants are grown by absorbing excess nutrients from the water;
Sump: the lowest point in the system where the water flows to and from which it is pumped back to the rearing tanks.
The above can be automated, with temperature monitoring and even solar-powered.
Aquaponic Gardening: Growing Fish and Vegetables Together.
Grow an entire dinner right in your backyard with aquaponics! Safe, healthy fish and organic vegetables with no weeds!
Where does the chicken fit in and why tilapia in particular
The five main things that an aquaponic system needs are water, oxygen, light, feed given to the aquatic animals, and electricity to pump, filter, and oxygenate the water (this is where the solar comes in).
The chicken shed above the fish provides the feed. Duckweed which grows in the pond can be used to feed the chickens. Here is a sketch built in a swimming pool:
Freshwater fish are the most common aquatic animal raised using aquaponics due to their ability to tolerate crowding, although freshwater crayfish and prawns are also sometimes used. In practice, tilapia are the most popular fish for home and commercial projects that are intended to raise edible fish because it is a warmwater fish species that can tolerate crowding and changing water conditions.
If you do not want to raise fish for edible purposes you can also raise koi and goldfish this way which can be resold to be kept as pets.
If you do not want to use chickens, and just use a traditional aquaponics system, the fish is then fed fish meal which is ground dried fish usually from a lower-value species fish will then poop providing your veggies with the nutrients to grow. This is probably the best way to start until you understand the system.
The financial case
Aquaponics allows farmers to grow vegetables and raise fish at the same time. By having two sources of profit, farmers can continue to earn money even if the market for either fish or plants goes through a low cycle. With the chickens added you can become a triple threat, even a quadruple threat if you factor in chickens provide both meat and eggs.
The flexibility of an aquaponic system allows it to grow a large variety of crops including ordinary vegetables, herbs, flowers and aquatic plants to cater to a broad spectrum of consumers. Herbs, lettuce and speciality greens such as basil or spinach are especially well suited for aquaponic systems due to their low nutritional needs.
The political case
If you have been reading me for a while, you will know that I am a realist. Some people look at the shiny side of South Africa (which only makes up a tiny fraction) and try to find solutions, often sourced from a well developed western country. The vast majority in South Africa live in dire poverty no different than overpopulated rural Asian towns. Those are better places to compare South Africa to, chicken aquaponics is a solution from one of those places.
The South African way
The most popular DIY South African aquaponics system that I have seen is the “drum system” also known as barrel aquaponics. I have seen this in back yards in Cape Town, in fact I saw one today, which inspired me to write this.
Why the barrel system
The barrel system is a modular way of aquaponic farming with a small footprint, you can easily add more capacity. Each four half drums is on a stand positioned above the fish tank or pond. The downside to this is that it is a bit expensive as each needs its own system (unless they can share a filtration system) and four half drums are not very large and do not produce a lot of veggies. There is another benefit to this system, and this is an important benefit, it deals with the fish stocking strategy. Wikipedia explains:
In order for aquaponic systems to be financially successful and make a profit whilst also covering its operating expenses, the hydroponic plant components and fish rearing components need to almost constantly be at maximum production capacity. To keep the bio-mass of fish in the system at its maximum (without limiting fish growth), there are 3 main stocking method that can help maintain this maximum.
- Sequential rearing: Multiple age groups of fish share a rearing tank, and when an age group reaches market size they are selectively harvested and replaced with the same amount of fingerlings. Downsides to this method include stressing out the entire pool of fish during each harvest, missing fish resulting in a waste of food/space, and the difficulty of keeping accurate records with frequent harvests.
- Stock splitting: Large quantities of fingerlings are stocked at once and then split into two groups once the tank hits maximum capacity, which is easier to record and eliminates fish being “forgotten”. A stress-free way of doing this operation is via “swimways” that connect various rearing tanks and a series of hatches/moving screens/pumps that move the fish around.
- Multiple rearing units: Entire groups of fish are moved to larger rearing tanks once their current tank hits maximum capacity. Such systems usually have 2–4 tanks that share a filtration system, and when the largest tank is harvested, the other fish groups are each moved up into a bigger tank whilst the smallest tank is restocked with fingerlings. It is also common for there to be several rearing tanks yet no ways to move fish between them, which eliminates the labor of moving fish and allows each tank to be undisturbed during harvesting, even if the space usage is inefficient when the fish are fingerlings.
Ideally the bio-mass of fish in the rearing tanks doesn’t exceed 0.5 lbs/gallon, in order to reduce stress from crowding, efficiently feed the fish, and promote healthy growth.
With the barrel system, in which the multiple rearing strategy can be used, you can have a pond for various size fish, if you are growing and adding capacity on a monthly or bi-monthly basis, then some fish are going to be older and larger than the new fingerlings (juvenile fish) added, this is a benefit as you will have a consistent income and be able to add more systems as income improve.
The system I saw today differs from the one below, it is better in my opinion, the frame (the wood part below) is metal (square tubing) and the pond below was a spacious round pond, which you could see into. I would prefer to keep the fish in a pond than a barrel (second photo below).
If you can’t find barrels or it’s too expensive to source, you can use a wood built system. This can also be scaled/capacity added to like the barrels:
Image credits: Ryan Somma, originhydroponics, howtoaquaponic, charlie vinz