Plants grow in soilless coirs made from coconut husks and get nutrients from the water.

Aquaponics combines fish and crops for a productive retirement

There is something fishy about a guy who doesn’t golf or watch television, at least in the case of Doug Blackburn. With those two traditional staples of retirement time use not an option, Doug set to work a few years ago to find a way to pass the time as he approached his departure from the work force.

He started looking into agricultural options that would be a fit on his small Union County farm. Through the years he had cattle, sheep and even emus, but he was looking for something different in his retired years.

He initially considered hydroponic plant production, but did not like the idea of bringing in nutrients all the time to meet the plants’ needs. He kept investigating and found a modern take on an ancient practice that interested him — aquaponics.

“I saw a YouTube video on it and I really liked the idea,” Doug said. “The Mayans did this thousands of years ago in Mexico and the Chinese did this 2,000 years ago.”

Aquaponics operates on the fairly simple notion that fish give off ammonia as a waste product, and then a type of bacteria in the water converts the ammonia into nitrites. A second type of bacteria in the water converts the nitrites into nitrates, which can be used in the production of crops.

James Rakocy, from the University of the Virgin Islands, researched and developed the use of deep water culture hydroponic plant production in more efficient large-scale aquaponics systems pairing tropical plants and tilapia that works particularly well in warm climates. Doug studied some examples of the system and adapted it to work in Ohio’s climate. He found that both native Ohio perch and lettuce thrive at 65 degrees, which is much better suited for Ohio’s climate.

“Perch and lettuce need the same temperature and there is a ready market for it here and they grow fast,” Doug said.

After learning more about the challenges and benefits of aquaponics, Doug and his wife Jeni jumped right into their new pre-retirement farm adventure — Fresh Harvest Farm.

“Neither one of us had the feeling that this wouldn’t work out,” Jeni said. “We just built it.”

There were some initial challenges when the Blackburns got into aquaponics three years ago.

“There was a steep learning curve. It is recommended that you start small and learn,” Doug said. “I started big and my mistakes were expensive.”

They built a 35-foot by 72-foot greenhouse with a 1,400-gallon fish tank and got started. Once the hose was left in the tank after filling it up and it syphoned all of the water back out and killed the fish. Things were also touch and go for a while due to a big unknown with the water from the well. After building the system, they tested the water quality with a few goldfish.

“Ideal well water has less than 1 part per million non-ferrous iron and no ferrous iron,” Doug said. “You also need the right calcium magnesium ratio and the pH needs to be close to 7. Sulfur water is also a problem. The goldfish were fine. We were fortunate that the water here was just right.”

With the right balance in the system, they can let the bacteria and the fish do their jobs. The water must be cycled out of the fish tank and through the plant grow beds once every hour. The fish tank is round so the fish cannot get trapped in the corners, where they can become sick and die.

“The water constantly swirls so the fish are always moving and they don’t know they are in a tank,” Doug said. “We use aerators in the fish tank and the plant beds to maintain 6 parts per million of oxygen

Doug and Jeni Blackburn feed crops starting with ammonia produced by perch in this Union County aquaponics greenhouse. The perch are in the tank to the left and the water is gravity fed to the crops.
Doug and Jeni Blackburn feed crops starting with ammonia produced by perch in this Union County aquaponics greenhouse. The perch are in the tank to the left and the water is gravity fed to the crops.

in the water.”

The tank holds roughly 1,300 perch that are raised there for 12 months to transform them from fingerlings to mature, full sized fish. They are fed commercial fish food that meets the needs of the carnivorous diet of the perch. They are purchased from a local fish farmer and re-sold to him after a year. From there, the fish are used for pond stock or processing. Some go to fishing ponds in Columbus.

Another challenge is that small perch produce much less ammonia than full sized perch, which can cause significant challenges in the carefully balanced production system. To address this problem, a second tank was added and new fish are brought in every six months to alternating tanks. This provides a more consistent ammonia supply.

The two types of bacteria used in the system grow naturally in ponds, but are added to the system initially to get it started faster. Even if everything goes perfectly right from the start, it takes time to get the system balanced properly.

“You have 6 to 8 months where your system is immature and your water is not stabilized,” Doug said. “When you first start you have an ammonia spike and then a nitrite spike, which can stress the fish, once the nitrates come along, the system starts to stabilize. At first we were testing the water twice a day, now we jut test once a month. Once it stabilizes it helps with your mistakes.

“A healthy aquaponic water is amber colored due to bacteria. It was neat to watch the amber color work its way through the system as it was growing. It took us 6 months to get the system to mature.”

The water system relies on one pump, but is mostly gravity fed. There is a sump pump below the fish tank that pumps the water up into the tank and it flows from there to the 1-foot deep grow beds that are in a series, with each progressive bed 1-inch lower than the previous bed. The nutrients in the water are fairly consistent throughout and the plants remove them as needed.

The plants are started and grown in coir growing medium made from the outer husks of coconuts.

“We started with just lettuce which is a good, fast crop to grow. Then, once you get going, every week you plant, transplant, and harvest lettuce crops,” Doug said. “When you have a fruiting crop you need to supplement calcium in the system. We use oyster shells.”

Now a variety of greens including 7 types of lettuce, Swiss chard, basil and two types of kale are grown year round in the greenhouse at 65 degrees. In the summer months there is enough sunlight to grow tomatoes, cucumbers, squash, and zucchini. The crops are grown with organic production methods, but are not certified. Beneficial insects are used for pest control, a garlic spray is used to control downy mildew and there are no weeds in the production system.

“I can’t spray pesticides because of the fish. Fish keep you honest. We can’t even add organic fertilizer to this system,” Doug said.

Lettuce heads are harvested after about 50 days. The plants with leaves that are harvested, like the basil and kale, are in production for about a year.

“After a year, the roots get too big and clog up troughs and create anaerobic issues that raise pH and ammonia,” Doug said.

Doug focuses on the production while Jeni markets the crops that make the money for the facility.

“The fish pay for themselves and generate some income, but the crops are playing the bills,” she said. “We can’t supply our demand. We have had to turn customers away. We have so many people who want local, pesticide-free fresh produce.”

The perch provide the ammonia that is transformed into nitrates by bacteria in the water.
The perch provide the ammonia that is transformed into nitrates by bacteria in the water.

Jeni sells the products at three Columbus area farmers markets and at her workplace in Columbus. She also created the popular “lettuce club” where customers pay an upfront membership fee and get a weekly share of the harvest. A share of the summer crops can be added for an additional fee. In addition, Jeni sells produce through an online farmers market in Champaign County where customers place their orders online and the products are delivered to a pick-up location.

“We also sell to restaurant vendors, including Harvest Pizzeria in German Village that wants Tuscan Kale,” she said. “It was a learning process for them to tell us a season ahead what they want us to grow for them.”

Customers love the fresh, high quality products from Fresh Harvest Farm. The crops are either harvested the previous night or the morning of delivery. The aquaponically grown lettuce is harvested roots and all, so it is actively growing right up until it is cut and sold to the customer.

“I get to talk to so many people who love our lettuce,” Jeni said. “They tell us they don’t even have to put dressing on our lettuce because there is so much flavor.”

The trick has been to stabilize production for a steady supply.

“The biggest challenge is to grow the right amount of produce at the right times,” Doug said. “But once the system is set, it sort of manages itself.”

With stabilized production and sound marketing, the aquaponic system should be profitable after 3 to 5 years. There have been challenges, but the unique production in Ohio offers many rewards, including numerous opportunities for tours and educating others about what it takes to produce food.

“This summer we helped with a program through the George Washington Carver Food Research Institute through St. Stephens Community House in Columbus,” Jeni said. “Four students in the program came here and worked on the farm for a week learn about food and where it comes from.”

With about a year remaining before he can retire, and no time for golf and television, Doug and Jeni are perfectly content with being a little fishy because of the many unique advantages of aquaponic production.

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  1. AQUAPONICS – After several months accumulating and selecting Web reference material for my daughter, I have about 40 pages of good information.

    Anyone wanting this data to prevent serious errors starting may send me an email requesting the files at no cost. This is not a business.

    Marvin A. Hodges
    San Diego, CA

  2. Please send the info. I am starting the tanks . Any info is appciated sincerly Connie Peruski

  3. Please send me your info on aquaponics.
    My wife and I are starting plans for a new house and would like to tailor the design to have an aquaponics system.
    Thanks for the fascinating read and inspiration.

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  10. Just getting started in Ohio. Would love to have the info you have collected. Thank you in advance.

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