RASTECH Magazine

Opinion Aquaponics Education Research
Discovering aquaponics

August 19, 2019  By Michael Ben Timmons

Jessie Powell, a senior in Biological and Environmental Engineering at Cornell University, shows off her team’s strawberry project.

I hope your summer is off to a good start. Mine is. I’m involved in a large indoor project producing 400 tons per year of salmon using mixed cell raceways (see my article in the RAStech 2019 spring issue). But my focus for this article will be aquaponics.

For the last 30 years (until about five years ago) I used to roll my eyes when anyone would mention aquaponics and the great results they were obtaining. According to these early aquaponics zealots they were getting more growth, better tasting plants, longer shelf life, better color, etc. Often, these comments would be from someone who was taking my hands-on short course (now available as a distance course, wee www.eCornell.com/fish). Since I try to be a polite and kind person, I would not ‘laugh’ out loud when hearing these comments. But, generally responded with some comments or questions such as, “Did you have any replications or controls to compare your results against?” Always, the answer was “Well no…but… my aquaponics plant production is just fabulous!”

Cornell has been one of the leaders in Controlled Environment Agriculture (CEA) for 50 years. The engineering professor (Dr. Lou Albright) and plant science professor (Dr. Robert Langhans) would always agree on one thing: if you take two complicated systems (RAS and hydroponics) and you put them together (aquaponics), then you have a really complicated system. And that no one in their right mind would do this.


Well, that all changed for me about six years ago.

I started conducting replicated and controlled research under commercial scale conditions. The hydroponic growing condition requires very careful and precise control of pH (around 5.8) and the macro and micro nutrients. RAS conditions generally target a pH value of 7.0. The problem is that if you were to run the hydroponic system at a pH of 7.0, you would cause very significant decreases in nutrient availability for many of the key elements. Well, surprise, surprise to all of us. Our results for bibb lettuce, spinach, and now strawberries are showing no significant differences in productivity between the aquaponic and hydroponic (pH 5.8) conditions. But the hydroponic system that operated at pH 7.0 had typical reductions in productivity of ~25 per cent. We have yet to figure out why. Our initial hypothesis was that it was the living microbial community from the RAS being given to the aquaponics plants that was providing the compensation to normal growth we had observed.

Being good scientists, we then ran a trial where we compared hydroponic (pH 5.8 and 7.0), aquaponic water, and sterile aquaponics source water (we auto-claved the fish water). Again, to our surprise (it seems this happens a lot to me), the hydroponic pH 5.8 and both aquaponic water conditions (autoclaved and non-autoclaved) all performed the same. (The hydroponic pH 7.0 again had very poor performance). So there apparently is some bacterial action that makes the nutrients more bio-available to the plants, but this conditioning occurs before the water is introduced to the plants. This makes running decoupled aquaponic systems totally available to the design team and farmer. (Decoupled aquaponics is where the plant system and the fish system do not recirculate water between the two systems.)

We are really happy with our strawberry aquaponic research. We are testing aquaponic vs. hyroponic using day-neutral strawberries (Albion and Monterey) since it is hard to compete in the summer with field grown berries, but in the winter the grower could obtain premium pricing. One of our student team leaders, Jessie Powell, senior in Biological and Environmental Engineering, Cornell University, on the strawberry project is shown in the image. Here are the papers we have recently published on aquaponics.

    Vandam, D.A.; Anderson, T.S.; de Villiers, D.; Timmons, M.B. Growth and Tissue Elemental Composition Response of Spinach (Spinacia oleracea) to Hydroponic and Aquaponic Water Quality Conditions. Horticulturae 2017, 3, 32.
  • Anderson, T.S.; Martini, M.R.; de Villiers, D.; Timmons, M.B. Growth and Tissue Elemental Composition Response of Butterhead Lettuce (Lactuca sativa, cv. Flandria) to Hydroponic Conditions at Different pH and Alkalinity. Horticulturae 2017, 3, 41.
  • Anderson, T.S.; de Villiers, D.; Timmons, M.B. Growth and Tissue Elemental Composition Response of Butterhead Lettuce (Lactuca sativa, cv. Flandria) to Hydroponic and Aquaponic Conditions. Horticulturae 2017, 3, 43.
  • Wielgosz, Z.J., Anderson, T.S., Timmons, M.B. Microbial effects on the production of aquaponically grown lettuce. Horticulturae 2017, 3(3), 46.

Michael Ben Timmons is a professor in the Department of Biological and Environmental Engineering at Cornell University in Ithaca, NY. He teaches information related to the production of aquacultured products with emphasis on sustainable and environmentally friendly engineering technologies.

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