Aquaponics = aquaculture (the raising of edible fish) + hydroponics (growing vegetables and herbs without soil). You may have seen examples of this revolutionary way of growing food in some of the projects featured on Inhabitat. Per square foot, it’s the most productive form of agriculture on the planet, and is a perfect example of a living machine: a self-sufficient assembly of plants and animals that functions like an ecosystem, producing food for people without creating waste products or pollution.
If you’re inspired to try out an aquaponic system instead of a vegetable garden in your backyard this summer, this guide will serve as an overview, giving you all the information necessary to get started. It’s a bit more involved than a typical vegetable garden, but anyone with a little mechanical ingenuity and determination can make it happen. If you feel timid, we suggest starting small to refine your technique before scaling up to a system that can feed the family (if not the neighborhood).
Every aquaponic system will include the components listed below. There are many options to add on to these and customize the system, depending on your particular circumstances and goals. For example, most people in cold climates will opt to build their aquaponics system in a greenhouse to keep it going year-round.
Image via Milkwood, on Flickr Creative Commons
In theory, a well-tuned aquaponics system can support one pound of fish per gallon of water. When starting out, however, it’s better to plan on stocking one fish for every 10 gallons of water to make sure the system doesn’t fall out of balance (plus the fish will have more space in which to swim).
Most do-it-yourselfers start with either a 55-gallon barrel or a 225-gallon square bin; two standard sizes of food-grade tanks that are fairly easy to come by recycled from the food industry. Just make sure they were used to hold benign things like soy sauce, rather than something toxic that might have left a residue. Aboveground vinyl swimming pools are the top DIY choice for larger tanks.
Image via Wikimedia Creative Commons
Your vegetables will need some type of water-resistant container to house the soilless medium that they’ll be grown in. There are many products available for this purpose, but there are just as many DIY approaches. The simplest route is to build shallow wooden boxes (6 to 10 inches deep), just like ordinary raised beds for vegetables, and line them with pond liner.
Each bed is then filled with an inert growing medium, such as perlite (which is super light, allowing the beds to be elevated off the ground) or fine gravel from your local landscape supplier (inexpensive, but heavy). Coco coir is the fanciest growing medium available and is often used by professionals for its ability to retain air and moisture simultaneously. A mixture of equal parts of all three products is actually a great formula to try.
You can plan to ferti-gate a growing area up to 10 times the surface are of your fish tank.
Pumps and Hardware
The miracle of aquaponics is that the plants (along with their growing medium) filter out the waste products from the fish tank, allowing them to thrive without ever adding fresh water, while the nutrients in the wastewater are the perfect fertilizer for most herbs and vegetables. Thus, a pump is needed to circulate the water between the two components and to make the self-sustaining system go round. If you choose to install a solar-powered pump, your aquaponics system will be almost entirely self-sufficient.
Pumps and piping are where aquaponics can get a little tricky; if you don’t have basic plumbing and electrical skills, find a friend that does to save on the amount of trial and error you subject yourself to. The pump can either collect the water that drains from the grow beds and put it back in the tank (if the grow beds are below the tank), or it can be placed in the bottom of the tank and used to spread the water over the surface of the grow beds (if they are elevated above the level of the tank).
The beds themselves need a network of PVC pipes on the surface to distribute the water from the fish tank. Drill ¼-inch holes every 6 inches in the pipe and structure the beds with several parallel pipes, each about 12 inches apart. You can plant the a seedling at each of the little holes in the PVC pipe.
There is one more absolutely critical piece of hardware to make an aquaponics system work: you need an aerator to provide sufficient oxygen for the fish.
Tilapia are by far the most common species used in small scale aquaculture systems. They’re a tropical species, however, and need the water temperature to stay between 70 and 90 degrees to stay healthy and grow quickly. They’re used for their tolerance of high stocking densities and less-than-perfect water conditions, plus they have a phenomenal growth rate, reaching a harvestable size of one pound in 6 to 8 months. Thus in a temperate climate, it is possible to stock the tank with fingerlings in May and harvest the ‘crop’ in October.
Catfish are also very amenable to high-density recirculating aquaculture systems and have no problem overwintering in all but the coldest climates, though they only put on growth when the water is warm. Yellow perch are the third most common species used in aquaponics systems, and have the advantage of being able to put on growth in cooler waters.
Some food plants are easier to grow in an aquaponics system than others. Basically, anything that is harvested as a leaf—lettuce, kale, arugula, spinach, basil, dill, etc.—responds very well to the nutrients found in fish water and can usually be grown without added nutritional supplements. It is also possible to cultivate species grown for their fruit, such as blueberries, strawberries, raspberries, etc., as well as vegetables like tomatoes, cucumbers and zucchini, but these typically require supplemental fertilizers, which are available from hydroponic suppliers.
Putting a System Together
You will need a flat, sunny space to set up your aquaponics system. If you’re not building it inside a greenhouse, you’ll want to get everything together in early spring, so you can stock the fish as soon as the water temperature hits 70 degrees. Stock the fingerlings first and start seedlings in flats of potting soil at the same time. By the time the seedlings are big enough to transplant, the fish should be producing enough waste to support the growth in the grow beds. Incidentally, the vegetables themselves have very little to do with cleaning the water for the fish—this actually occurs in the growing medium, so the water needs to circulate through the grow beds for the sake of the fish, whether there are plants growing in them or not.
Management and Fine-Tuning
The aerator needs to run 24/7 to provide oxygen to the fish. The pump that moves water from the tank to the grow beds should be on a timer that turns it on for short periods of time, several times a day. You’ll have to experiment with the frequency and length of watering: the goal is to run it as much as possible to keep the water clean for the fish, but you’ll have to limit it to prevent the growing medium from remaining excessively wet.
The fish are typically fed as much food as they can consume in 20 minutes three times per day (click here for one of the only suppliers in the country of organic fish food). There are automatic feeders and many other optional components that can streamline and automate the system, which can make the feeding process a lot easier. The key is to start small and simple and to not push the system too hard by overstocking the fish. Overfeeding the fish is the easiest mistake to make and will quickly result in degraded water conditions. Once you have a simple system and an established routine that works for you, build on your success by expanding your system.