Small Green Food Machine
Imagine if you could produce your own fresh food in a small space and do it in an environmentally friendly and inexpensive way. Using aquaponics (a combination of aquaculture and hydroponics) you can!
Fish are kept in a tank with grow beds elevated around them. Water from the fish is used to irrigate and fertilize the plants. The root systems of the plants and the growing medium remove nitrates from the water to use as food. The water is then returned by gravity to the fish tank, aerating the water as it falls into the tank. This system is organic and saves water.
There are many ways to practice aquaponics; from small home aquarium tanks with a few salad greens growing in the inverted lid to warehouse sized commercial operations. My family and I built a small system from all found and recycled materials. It is watered by hand (30 minutes labor per day) so it does not use electricity. It takes up about one and a half square meters of space.
The idea for this system came to me after some repairs had been done on the highway near where we live. The road crews had left behind a broken piece of culvert and a small pile of pea gravel. Reduce, Reuse, Recycle! I knew that the culvert could be used as a fish tank with a little cement work so we carted it and the gravel home.
The first step was to create a base for the tank using chicken wire and cement left over from a previous project. The tank was placed on the base and sealed in place. Then the tank was then filled with water from our well. If you use chlorinated city water remember to wait a week or so before putting fish in the system, this will allow the chlorine time to dissipate. Tilapia fry from one of our aquaculture tanks were placed in the tank and began the process of fertilizing the water. The only input into this aquaponic system is food for the fish. If you use an omnivorous fish like tilapia all of their food can be grown for them. Duckweed is an excellent complete diet for tilapia.
We collected used plastic containers from our village school and clinic. The tops were cut off and the containers washed very thoroughly three times. Then a hole was made in the side of each containers base using an awl to allow water to drain back to the tank. An old board from the plant nursery was given new life as the shelf for the containers. It is more common in aquaponics to use large growing beds but we were going with what we had or could source for free. The containers were filled with a mix of coconut fiber and rice husk because those are materials readily available for free where I live. If you use coconut product you need to use chips and fiber, not the powdered coir soil amendment. If you are not sure of the source it should be soaked and rinsed very well as it may have a high salt content. Coco chips are excellent in a hand powered aquaponic or hydroponic systems as they retain moisture very well while still having adequate air spaces for the plant roots.
Lettuce seeds were placed in the containers and a layer of pea gravel was placed on top so that everything would not wash away when watered by flooding the containers.
Ten days later and looking good! (above)
The ‘free’ aquaponics system has been providing us with fresh greens and fish for six months now and will keep doing so for the foreseeable future.
Aquaponics meets all of the criteria for sustainable agriculture. It is environmentally sound, has minimum inputs, and is socially responsible and economically viable.
If you have been thinking of producing more of your own food aquaponics is one good way to go about it!
How to Build a Small Aquaponics System from Recycled and Found Materials
To build a small hand powered aquaponics system you need the following items -
- a tank to hold the fish
- a container(s) for plants
- some means to elevate the plants above the fish tank
- a watering device
Let’s go through how the system discussed in the article was built and then have a look at some alternative ways of doing things.
1- A base was created for the concrete culvert using cement and chicken wire left over from a previous project.
2- The concrete culvert (tank) was placed on the base and sealed in place with cement.
3- Fish were placed in the tank to fertilize the water
4- An old board was placed over the tank.
5- Recycled plastic containers were cut to size.
6- An awl was used to punch a drainage hole near the bottom of the containers. This will allow cleaned water to fall back into the tank. On the opposite side of the containers, near the top, a hole was punched to allow two containers to be connected using string. Doing this increases the amount of containers that can be placed on the board, if desired.
7- The containers were filled with a mix of rice husk and coconut fiber.
8- Seeds were planted and gravel was placed on top to prevent the contents from floating out of the container when flooded during watering. Seedlings grown using hydroponic media could also be used instead of seeds.
9- The containers were placed on the board so that their drainage holes allow water to fall back into the tank.
10- The containers were flooded with water from the tank using a watering can without its showerhead.
Tips on Start Up and Maintenance of the System
1- Place your fish in the tank at least a week before you add plants to the system to allow them time to fertilize the water. In a system this size we have found no need to cycle water through the growing media before planting but many sources advise you to do this.
2- Before watering your plants swirl your hands gently through the water in order to put fish waste into suspension before filling the watering can. At some point you may find that you have an accumulation of waste. Move the fish to a temporary container, using the water from the tank, clean out the tank and return the fish and water.
3- Flood your containers three times a day or more.
4- Feed fish according to age and type.
5- The water in the tank will need to be topped up because of evaporation. The best way to do this is with a strong spray. This fills up the tank and provides extra aeration for the fish.
Anything that holds water well can be used as a fish tank. Some ideas are large plastic tubs (see photo), pre-cast fiberglass tanks and solid sided children’s wading pools. If you make your system portable (with the water removed) you could even use it indoors with the addition of grow lights. Good for those of you in cold, snowy locations!
Plants can be grown in a single large container, several medium sized ones or many small ones. Use your imagination!
Aquaponics provides you with an environmentally friendly way to raise fish and plants in a confined space. A hand powered system uses no electricity and minimal water. All fertilizer is provided organically by the fish. A system like this is very helpful in teaching children how an integrated ecosystem (Planet Earth!) functions.
I find watching the fish and tending the plants very relaxing. I also love to eat the fresh produce and fillets that the system produces. Bon Appetit!
Temperate Climate Considerations
Here in Thailand we need protection from torrential monsoon rains and also from 40c+ temperatures. In temperate climates you will need protection from frost and cold.
You can see from the photo of our system that there is a framework of ¾ inch pvc piping over it. This was made from bits of pipe and junctions left over from a greenhouse project. We use the frame to hold plastic sheeting in the monsoon season and shade net in the very hot season. In a temperate climate such as most of the UK and the southern US a single layer of thick plastic sheeting might suffice for plant protection. In colder climates a small greenhouse structure would be more appropriate. Free information and plans for building greenhouses are widely available on the internet.
Plants and Fish
The types of plants that will grow in a garden are largely dependent on that gardens location. Any plants that you are already growing successfully should do well in an aquaponics system. Water loving plants such as lettuce and other greens do very well in an aquaponic garden.
Fish can be very temperature sensitive so it is best if you find out which types of fish do best in your climate. In almost all locations a nearby fish hatchery should be able to provide both information and fish fry or fingerlings.
If you live in a really cold location consider making your system portable so that you can take it inside during the winter. Use of a plastic or fiberglass tank instead of concrete and the addition of grow lights make aquaponics possible all year round regardless of your location!
Hydroponics supplies are available from shops in most locations and also on the internet. Hydroponic equipment can be used for building an aquaponics system; the BIG difference is that you are feeding your plants with organic fish waste, not a soup of nasty chemicals. Tasty fish to eat too!
Aquarium shops also have equipment that can be used for aquaponics.
The internet is a good source of free 'how to' information on aquaponic systems.
Aquaponics is a sustainable, eco friendly food production system that is in use from Antarctica to the Arctic circle and from the deserts of Arabia to the jungles of Thailand.
This is the future of food production!