Aquaponics systems are revolutionizing the way we grow food commercially and at home. These systems, which fertilize plants with the waste byproducts of fish, allow food to be grown regardless of rainfall, soil quality, fertilizer or pests. Research has shown that an aquaponics system uses about just a tenth of the water used to grow vegetables in the ground, making this kind of setup a perfect solution for arid regions, areas prone to drought, or for indoor gardening systems.
How Aquaponics Works
In an aquaponics system, fish produce ammonia-rich waste that breaks down into nitrites and eventually nitrates that plants love. A pump takes the water from the fish tank to a grow bed, where plants grow in peat moss or gravel. The nutrients from the fish waste fertilize the plants, while their roots further filter the water for the fish in the tank. From the grow bed, water recirculates to the fish tank and the process begins again. The whole system oxygenates itself through the percolation of the water and an (optional) air pump.
What Does It Cost?
Aquaponics setups provide one of the cheapest ways to cultivate food. Costs range from less than $50 for a tiny kitchen counter setup to around $400 and up for a large kit. Of course, the more you’re willing to upcyle or buy second hand, the cheaper it gets. If you tally up what you spend in a year on salad greens and herbs (or the produce of your choice), you're likely to find this mini-farm is an insanely safe investment. And while the materials list is a bit daunting, the process is anything but.
How To Build Your Own Aquaponics System
- Fish tank (at least 40 gallons if you want to raise edible fish)
- Fish tank filter system (Two corner filters will do a great job circulating the water. For my 70-gallon tank, I've used two Whisper 40i Internal Power Filters by Tetra for five years without incident)
- Gravel for the bottom of the tank
- Grow bed for plants (as basic as any watertight container or as complex as an industrial planting bed from a gardening store. Make sure it is large enough to sit flat on top of your fish tank without falling in.)
- Water pump (the smallest pond pump you can find and compatible clear tubing to run from the pump to the grow bed - I use ½-inch tubing cut to appropriate length)
- Pea gravel (for the grow bed)
- Fluorescent grow light (these come in varying strengths and sizes—check on how much light you'll need for the plants you want to grow)
- Stand for fluorescent light (or build your own)
- Light timer (optional)
- Fish (Most people recommend starting out with feeder fish or minnows; then, once you're sure your pH is all set, to switch to whatever fish you like. Tilapia, trout, carp and largemouth bass are most often recommended if you'd like to raise edible fish in the tank.)
- pH test kit
- Nitrogen test kit
- Seeds (Easiest for aquaponics newbies are salad greens and herbs: spinach, lettuce, mesclun, mustard and any other organic greens you can find.)
- Set up your tank (not your grow bed yet!) with gravel in the bottom, a few items like castles or water plants with nooks and crannies for fish to hang out, and water to the top. Let the tank circulate for two to four days to allow chemicals like chlorine to work their way out of the system.
- Add fish. The gold rule of aquariums is one inch of fish for every gallon of water you have. Remember that fish will grow! Some of the fish will inevitably die. When they do, leave them floating in the water. As the feeder fish break down, they'll become ammonia-based waste. Bacteria will slowly colonize and turn ammonia into nitrite (ammonia and nitrite are both toxic to plants). After that, more bacteria will colonize and change nitrite into nitrate, which is usable fertilizer for your grow bed.
- Let the system grow into itself. Execute weekly nitrogen and pH tests until everything is optimal (40-80 ppm for nitrogen levels; ideal pH levels depend on what kind of fish you have in the tank).
- Set up your grow bed. Place the container flat on top of the fish tank, then prop up one end with a piece of wood (1x1 inch or 2x2 inches is fine) to allow gravity to pull water across the bed. At the low end, drill holes through the container to allow water to drain. Fill the container with many smaller plastic pots of pea gravel (this will make for easier cleaning), or fill the entire container with three to six inches of pea gravel.
- Set up the light. If your light didn't come with a stand, build a basic box frame out of scrap wood and secure it to the surface supporting the fish tank.
- Hook up the water pump and tubing. The lower in the tank, the better for the pump and the more you'll filter. Make sure you have enough tubing to get from the pump all the way up to the highest part of your grow bed. Turn the pump on, adjust the speed of your pump accordingly, and let the whole system run for 24 to 48 hours in order to troubleshoot any issues.
- Plant your seeds. For salad greens, simply sprinkle the seeds evenly over the pea gravel in your grow bed. For other plants such as tomatoes, proper spacing (and regular trimming!) will be necessary.
- As a standard rule for most plants, you should have your grow light on for 12 hours, off for 12 hours. As you progress and want to experiment with blooming or fruiting plants, lighting will have to be adjusted accordingly.
- Feed your fish daily, keeping in mind that a healthy fish will consume around 1.5 percent of his or her body weight each day. Do not overfeed!
- Check your pH and nitrogen levels monthly.
- Clean your filtration system and tubing regularly. Most tank filters recommend monthly cleanings, however you will find with all the filtration happening in your grow bed (and with appropriate feeding levels for your fish) that you will likely only need to clean out your system a few times a year.
- Trim or harvest plants as needed with sharp scissors. Leaving roots intact will allow new vegetation to grow.