How to Automate Your Vegetable Garden With Aquaponics
Me and my wife have two kids and we both work full-time. We strongly believe in home grown produce and serving healthy and nutritious food on our dinner table. After we moved to a house with a large backyard, we decided it was time to start growing our own fruits and vegetables. Later that year, we created our first vegetable garden.
But something happened we did not expect. Maintaining a vegetable garden was more work than we had thought and our first harvest was a big failure. We were both disappointed and thought about pulling the plug on the entire project. I started checking websites on the internet, trying to find a way to get better at growing vegetables, and that’s when I unwillingly stumbled on to aquaponics
What is Aquaponics?
Aquaponics is the perfect marriage between two food producing systems. First, we have hydroponics. This is the growing of plants in a soilless environment, the vegetables are not planted in sand but in gravel, vermiculite or clay pebbles. Nutrient rich water is pumped through the medium allowing the roots of the plants to absorb what they need. Second, we have aquaculture, the production of fresh-water fish in large fish tanks. Both of these systems have flaws, but when combining them, we can overcome these difficulties and produce high quality vegetables.
You see, hydroponics, is a closed system. Synthetic fertilizers are added to the water tanks and this water is pumped through the system where the plants are located. The plants absorb the water and nutrients they need and the remaining water flows back to the tanks, after which the process is repeated over and over again. Not every element is absorbed by the plants and sometimes there can be a build-up of a certain chemical, requiring the farmer to dump (part of) the water and start over again with fresh water. The dirty water is often released into nature and causes damage to the environment.
Aquaculture is a closed system as well. Water is pumped from the fish tanks into a filtration system, to clean the water and provide the fish with a healthy environment to grow in. Food residue and fish waste can build up in the system and water has to be released into nature in order for the fish to be safe. This dirty water can cause damage to the environment as well.
Aquaponics is the combination of these two systems. Instead of adding chemicals to the water to feed the plants, we use the natural fish waste to feed our plants. This way, the plants act as a filtration system, providing the fish with healthy, clean water. This closed loop system can still be at danger to build-ups. Our first priority is to grow plants, we can stop feeding the fish for a few days, allowing the levels to return to normal. You see, the problem with hydroponics and aquaculture is that they are created to earn a profit. It’s in the farmer’s best interest to grow food as quickly as possible. Dumping the water is more profitable than to stop feeding the plants or the fish for a few days, which will slow down growth.
For us it doesn’t matter if the process takes a bit longer, our first priority is to grow healthy produce.
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Planning Your First System
As mentioned before, aquaponics is a closed system, pumping water from one tank to the grow beds and letting gravity return the water to the fishtank. Setting this up correctly is important. A leak, or a tank that overflows can cause your water to drain from the system, killing your fish and destroying your plants. This is in fact the trickiest part of the build. You can add a drain at the bottom of the growbed, but if this hole is too large, the pump will not be able to fill the growbed enough for the water to get to the roots. If the drain is too small, the pump will eventually make the growbed overflow, reducing the water lever in your fishtank.
Solution 1: Deep Water Culture of DWC
Deep Water Culture or DWC removes the medium from the system completely. The plants are placed on a piece of styrofoam that floats on the surface of the water. Holes are cut in the foam, allowing the roots of the plants to hang in the water. You add a drain at the top of the growbed, this will allow water to stay in the growbed at all times, but it will never overflow. Not all plants are suited for this technique as the roots of the plants are submerged at all times. Green leafy vegetables seem to do well in this kind of environment.
Solution 2: The Bell Syphon
This solution works for all kinds of vegetables. The plants can just remain in their medium like gravel or clay pebbles. Instead of a drain at the bottom of the growbed, a bell syphon is added to the growbed. The growbed slowly fills with water until a certain level is reached. The Bell syphon is activated and drains the growbed in a matter of seconds. When the growbed is empty, the Bell syphon stops, and the growbed starts filling up again. This process is repeated over and over again.
This method will provide the plants’ roots with water and nutrients at intervals, allowing air and oxygen to get to the roots as well. In my opinion this method works best for small, simple systems.
Building Your First Aquaponics System
I built my first system mostly with recycled materials and it was constructed following the flood and drain method, using a Bell syphon.
I searched the web for local used IBC containers and picked up two cheap ones a few miles from my house. This will be your growbed and fishtank, so make sure you know what product used to be in them. Anything food related or a water-soluble product will be safe. I cut one container in half, giving me two equally large growbeds. I found that 30 cm (about 1 foot) is an ideal depth for a growbed, so you might want to adjust the height of the growbeds before installing them.
The other IBC container was left intact as the fishtank, only the top part was cut open, allowing me easy access to the fish. All parts were cleaned, and cleaned again to make sure there was no toxic residue left in the tank or growbeds.
I constructed a raised table for my growbeds so they were higher than the fishtank, allowing gravity to return the water to the tank. This way, I only had to buy a single pump to put in the fishtank. I calculated the total volume of the fishtank and the growbeds and bought a pump that can turn over the entire volume in an hour or less.
I placed the pump in my fishtank and connected the outlet to a pipe that ran all the way to the growbeds. I placed one Bell syphon in each growbed and an emergency overflow back to the fishtank in case the bell syphons failed for some reason. The growbeds were filled with clay pebbles because they are quite cheap in my part of the world. You can also use gravel or vermiculite.
Now the time had come to plant my first vegetables and start pumping the water. Fish would be added three weeks later, because you need to allow bacteria to grow in the system before you add the fish. Don't rush this process and add fish anyway, the fish waste will not be broken down quickly enough and can cause the water to become toxic. The bacteria need to be fed though while there are no fish yet, so add some nutrients to the water every day until the fish are in. A little bit of urine will do the trick, but throwing in some fish food works just as well. I used liquid seaweed extract, a nutrient rich natural product, that is safe for fish.
A great book that helped me out when I was setting up my first aquaponics system.
- Get to know Aquaponics - Backyard Aquaponics
A great site, covering all kinds of aquaponics systems
The plants were thriving in this system, even on hot, dry summer days. They get water and nutrients every 15 minutes in, day or night. I used this system for 2 years before I started expanding and I was always amazed how fast the plants would grow. Once the growing season has come to an end, you can harvest the fish from the tank, gut them, clean them and put them in your freezer. Every season I would have around 50 fish to harvest, my freezer would fill up rather quickly in that time of year. You can use most types of fresh water fish like tilapia, silver perch, catfish or even trout. Tilapia is one of the easiest to grow, trout can be rather hard.