The symbiosis of fish farming and vegetable growing in a closed system, the so-called aquaponics, is on the rise in the Czech Republic. In order for business to be not only profitable, but also maximally ecological, it is necessary to balance a delicate balance in the system, which would suit both fish and plants. The researchers from the Brno University of Technology and the Institute of Global Change Research of the ASCR (CzechGlobe for short) have now come up with a solution. Together with Flenexa, they mapped the nutrient flow in the aquaponic farm, designed a model to predict the behaviour of the system and, according to the first laboratory tests, selected algae that should help make high-tech farming more efficient.

The Flenexa aquaponic farm in Přáslavice near Olomouc looks like a sci-fi film: in a four-storey underground bunker of a former military complex, salads grow under artificial light, the roots of which are in the water instead of clay, and fish swim in the tanks. However, Flenexa differs from conventional aquaponic farms. In addition to its own cultivation, this technology company solves the development of innovative equipment, which it supplies to others interested in aquaponic farming. They are also assisted in their research by experts from the Faculty of Mechanical Engineering at BUT and the Academy of Sciences, who have joined forces with the company in the framework of so-called innovation vouchers.

"The first collaboration focused on the analysis of the flow of matter and energy in the aquaponic process. Over the course of three months, we took and analysed dozens of water samples from the Flenexa farm. Thanks to this, we were able to map the flow of nutrients that travel primarily from fish towards plants, and we also created a model that can simulate what the system will look like after a change. In layman's terms: how will the balance of the system change if, for example, I harvest a certain amount of salads,” Vítězslav Máša from the Institute of Process Engineering, Faculty of Mechanical Engineering, Brno University of Technology, describes. Based on this model, the company is now preparing software that will offer customers to monitor their aquaponic farms.

The second step was to solve how to establish a nutrient balance in the system. This task was assigned to the scientists from the Institute of Global Change Research of the Academy of Sciences. "Our goal was to design a technology that would help remove excess nutrients, especially nitrates, that accumulate in the water. We selected and tested two types of algae and it turned out that nitrogen compounds are consumed very efficiently. Therefore, in the future, we are considering connecting an algal bioreactor to the circulating aquaponic water system. It can be imagined as a tube or a flat aquarium, which shines through and where growing algae acts as a stabilizing element of the whole process," Kateřina Sukačová from CzechGlobe explains.

Independently and ecologically

The described efforts lead to a kind of ideal of aquaponic farming, which is a maximally efficient and self-sufficient system, which – with a little imagination – could be a way to produce food in difficult conditions, such as in this case in an underground bunker. "We plan to use algae to maintain balance during system stock changes. In addition, they are in themselves a product that we want to try to use to feed fish, which would close the cycle even more. For the time being, our efforts for maximum independent farming are limited, for example, by the fact that we have to feed fish with commercially purchased feed. The current results are encouraging, although we consider it more of a starting point, we are certainly waiting for further development and cooperation with experts," Michal Netolický, the co-owner of Flenexa, says.

After all, they are working with engineers from BUT on another innovation, namely a special growing box for hydroponics (i.e. growing plants in water, but without fish), which would be completely self-sufficient. Today's aquaponic and hydroponic farms usually operate in specially adapted areas, where suitable lighting and air conditioning are installed. The new growing box should take care of all this itself. "We plan to use it for experimental purposes because we want to document hydroponic cultivation practices for other vegetables. Ideally, we would also like to sell it and the boxes will be designed so that they can be stacked, for example, in an empty storage hall equipped only with shelves. The boxes would be completely independent and the human staff would only ensure the planting and harvesting of already grown vegetables," Netolický adds to his vision.