The difference between aquaponics and hydroponics is that all of the nutrients going to the plants grown in water come from fish wastes that benefit in turn by their environment being cleansed by those same plants.
With a growing emphasis on organics and sustainability, farmers and gardeners are looking for new ways to grow successful crops with less need for space, irrigation and chemical fertilizer.
Deanna Outlaw of Evansville recently built her own small aquaponics system, which she plans to expand in coming years. Outlaw is a certified welder and is enrolled at USI for a degree in environmental science.
“Aquaponics is a symbiotic relationship between fish and plants,” she said. “The water from the fish tank with the fish waste gives nutrients to the plants, and in turn the plants and the growing bed cleanses the water before it goes back in with the fish.”
Aquaponics can be considered a subtype of hydroponics (plants grown in water, not soil), but is different in that plants grown hydroponically are usually fed with complex mixtures of chemicals added to the water. In aquaponics, all nutrients come from the fish.
It is especially beneficial in a system where fish or other seafood are being aquacultured as a food source.
In these operations, large quantities of water quickly become dirty and need to be filtered to remove accumulated waste, which can become an environmental hazard. By using aquaponics, the fish waste performs a useful function and the plants perform the filtering.
Outlaw isn’t yet raising fish for food, although she might in the future. She has 20 goldfish and two algae-eaters in a 110-gallon stock tank. Two pond pumps inside the tank pump the water through hoses up onto a platform, where it runs into four grow beds made of heavy duty plastic storage containers filled with pea gravel.
“The grow beds need to be higher than the fish tank because gravity makes the water drain back into the tank,” said Outlaw. “It’s a constant flood and drain. Originally I just had one pump but it wasn’t enough power to get water to all four grow beds, but if you had a really large pump you wouldn’t need two.”
Her platform and structure is shoulder-high, made with recycled wood pallets.
“The first thing we did was build the structure,” she said. “We had a bunch of pallets around so we used them. Then you have to get the fish tank ready, because the water needs to season. We had fish for a month before the water had enough nutrition in it to feed the plants.”
The fish are fed duckweed, which Outlaw grows in small tubs next to her grow beds, a balanced natural flaked or pelleted fish food, and occasionally, freeze-dried meal worms, lettuce or little pieces of vegetables. The algae eaters keep the tub free of algae, and between the water’s constant movement and the hungry fish, mosquito larva aren’t a problem.
To keep the water level in the grow beds constant, Outlaw drilled a hole in the middle of the bottom of each container and placed a PVC pipe through that is slightly shorter than the tub sides. To make the opening watertight, a washer was placed around the pipe inside the tub, and on the bottom where it would not touch the water. The edges of the hole were sealed with silicone caulk. The open pipe was topped with a bell siphon to keep foreign material out, and the tub filled with gravel. Below the tub, the drainage pipe leads back to the fish tank.
The grow beds are filled with well-cleaned pea gravel — no soil at all. “There’s about 500 pounds of gravel up there, even though it doesn’t look like it,” said Outlaw.
Once the system was running successfully, the plants could be added.
“We used bedding plants from Peckenpaughs (Garden Center),” said Outlaw. “If you start with plants and not seed, you have to thoroughly rinse the soil away from the roots. You don’t want the soil to get in the fish tank through he plumbing, and there’s a certain amount of plant food in the soil that you don’t want to get in the water for the fish. To start with seeds, just sprinkle the seeds on top of the gravel. We’ve started lettuce, spinach and carrots from seed. I knew that the water would come up and pull them down and I didn’t know if it would work, but sure enough they sprouted right up. “
Outlaw tests the water for pH and ammonia every three days. In aquaponics, pH is very important. Fish like a higher pH, and would be happy at a pH of 8. Vegetables are happier at around a pH of 7.2.
“Right now I’m at about a 7.4,” said Outlaw. “For awhile it was 8 and the plants weren’t blooming, so I slowly added a little lemon juice to alter the pH. If you do it too quickly, it will kill the fish. You want zero ammonia. It comes from the fish waste and urine. If you notice the ammonia spikes they are being fed too much.”
Larger operations often filter the water between the fish tanks and the grow beds, but Outlaw doesn’t mind fish waste solids getting into her grow beds, because they’re good for yet another beneficiary of her system — earthworms.
“The thing I found hardest to believe is that earthworms will live between the rocks actually in the water,” said Outlaw. “I thought I was going to be drowning and killing them, but someone swore to me they did fine and were beneficial, so I put a couple in one bed. They went right down into the rocks and I couldn’t see them, so I didn’t know right away what happened, but then later I was moving a tomato plant and there were a bunch of baby worms in the plant roots, about an eighth-of-an-inch long and bright magenta, so I knew they were surviving and doing well. … And also now the worms are eating the solids and the worm castings are good for the plants too.”
One might question why a gardener or farmer would go through all this trouble rather than just stick plants in the ground.
“One advantage is that plants tend to grow faster,” said Outlaw. “And you use fewer chemicals. With the plants away from the ground, you don’t really need pesticides and fungicides. If I see a bug, I just pick it off and throw it in the fish tank. You can do a lot more in a small space. You can plant very close together and the plants grow great. You use a lot less water. Every now and then I add a little to the tank to account for evaporation, but it’s a very small amount. Anyone can do this, even inside an apartment; with a small tank, small grow bed and a light, and you can grow all year. Outside, you can have it go all winter.
I’m going to put a heater in the water and cover the tank, put insulation under and up the sides of the structure and cover it with a transparent cover. I believe this is the farming of the future.”
Little Gem Salad with Lemon Vinaigrette
Source: Food and Wine, Contributed by Nancy Silverton
1 cup walnut halves
1 tablespoon walnut oil
– Kosher salt
1 small shallot, minced
1/4 cup fresh lemon juice
1 tablespoon Champagne vinegar
1/2 cup extra-virgin olive oil
– freshly ground pepper
4 ounces yellow squash, thinly sliced
3 thin red onion slices, separated into rings
4 heads Little Gem lettuce
1/4 cup freshly grated Pecorino Romano cheese, plus more for serving
1 Preheat the oven to 350 degrees. Toast the walnuts on a pie plate until golden, 12 minutes. Let cool, then coarsely chop the nuts. Transfer to a bowl and toss with the walnut oil and a pinch of salt. In a small bowl, combine the shallot, lemon juice and vinegar and season with salt. Let stand for 10 minutes. Slowly whisk in the olive oil and season with pepper.
2 In a large bowl, toss the squash with the onion, lettuce, walnuts, pecorino and half of the dressing and serve. Reserve the remaining dressing for another use.
Buttered Baby Carrots
Source: Adapted from Rachael Ray, “30 Minute Meals”
1 1/2 pounds baby carrots, cleaned
3 tablespoons butter, cut into small pats
1 tablespoon sugar
1 teaspoon coarse salt
— sprinkles white pepper and nutmeg to taste
1 Place baby carrots in ½-inch of water with butter, sugar, and salt. Bring water to a boil, cover pan, and reduce heat to simmer.
2 Cook carrots 7 or 8 minutes, remove lid, and raise heat to medium high. Add pepper and nutmeg, and reduce liquid until it almost evaporates, a couple of minutes. Turn carrots in sauce, taste to adjust seasonings and serve.
In aquaculture the water used gets polluted by the growing fish and needs to filtered. Instead of commercial filters to do the work, the water is introduced to plant roots which absorb the waste as food.The system was first recorded by the Aztec Indians of Mexico who perfected it to provide food for their large civilization. When a group of people don’t have to spend large amounts of time on procuring food then they are able to use the extra time to advance their culture.