A team of doctoral students from Mendel University in Brno is exploring a new use for waste generated by fish farming. They are developing FISHIT, a biostimulant made from fish sludge that promotes plant root growth, improves nutrient uptake, supports plant growth and vitality, and increases plant resilience. The project brings together students from MENDELU’s Faculty of AgriSciences and Faculty of Horticulture and could eventually benefit both home gardeners and agricultural growers.
The idea for the project emerged more than two years ago by linking the research topics of doctoral students at Mendel University. While Kateřina Patloková from MENDELU’s Faculty of Horticulture focuses on optimising plant nutrition in hydroponic systems and the use of biostimulants, Lukáš Harabiš from the Faculty of AgriSciences studies options for processing fish sludge, a by-product of intensive fish farming. “Fish sludge contains organically bound nutrients as well as a naturally occurring microbial community, and it would be a waste to regard it simply as refuse. We therefore began looking for a way to convert it through a controlled process into a liquid product that could be used in plant cultivation,” the project’s authors explained.
The research is being conducted primarily at the Department of Fisheries and Hydrobiology of MENDELU’s Faculty of AgriSciences, which operates recirculating aquaculture systems. The research team first identified the optimal method for using oxygen and microorganisms to break down the waste sludge produced by these systems. Another key question was whether the resulting product would be effective. The first large-scale trial was conducted on hydroponically grown basil, with part of the conventional mineral fertiliser replaced by the fish-sludge product. The plants achieved yields comparable to those obtained with standard mineral nutrition while developing a significantly larger root system—40.3% larger than that of the mineral-fertilised control plants.
The results suggested that the product was more than simply another liquid fertiliser. It also demonstrated a biostimulant effect, which was subsequently investigated in terms of its microbiological properties and content of biologically active compounds. A larger root system, together with beneficial microorganisms and biologically active compounds in the product, may improve water and nutrient uptake, promote plant growth and increase resistance to stress factors. The original experiment was therefore followed by a series of further growth trials. In a pot experiment with basil, plants treated with the highest concentration tested produced, on average, 27% more above-ground biomass than control plants watered only with water. “A statistically significant effect was also confirmed in the treatment using the sterilised product. This indicates that its effects are caused not only by the microorganisms it contains but also by biologically active compounds that occur naturally in the product,” Harabiš said.
Further testing was carried out on a wide range of plants, including leafy, root, bulb and fruiting vegetables, soft fruit and ornamental plants. Based on the results of these experiments, the team determined the optimal application method and dosage for each crop group. This information will subsequently be included on the product label.
As the project progressed, its authors also began exploring the research’s commercial potential, leading to the creation of the FISHIT brand, whose name refers to the product’s origins. The research team is currently working with the Tilapia s.r.o. fish farm, enabling it to verify the technology outside the laboratory and focus on practical aspects of future production. Over the coming months, the team will primarily monitor the repeatability of the process and the consistency of individual production batches under real operating conditions.
The product is suitable for a wide range of plants grown both in the ground and in containers. It can be applied as a soil drench or foliar spray and can also be used when rooting cuttings or as a supplement in hydroponic systems. As it is made entirely from natural materials, it can also be used in organic farming.
Another important milestone for the research team was its participation in the MENDELU Boost competition, which supports the transfer of research results into practice. In addition to developing the product itself, the team began addressing brand protection, the future business model, pricing, distribution and marketing. “FISHIT stopped being merely the working title of an experiment written in marker on a barrel a long time ago. It is now a functional product backed by university research, and we are working out how to get it from the laboratory into the hands of growers,” Patloková added.
Contact for further information: Ing. Lukáš Harabiš, Department of Fisheries and Hydrobiology, Faculty of AgriSciences, lukas.harabis@mendelu.cz, +420 733 280 506; Ing. et Ing. Kateřina Patloková, Department of Vegetable Sciences and Floriculture, Faculty of Horticulture, katerina.patlokova@mendelu.cz