This study was carried out to assess the biotechnical and limnological effects of different growth media in a Pyramid Nutrient Film (PNF) Aquaponic System on Giant African catfish (Heterobranchus bidorsalis) and tomato (Lycopersicum esculentum) raised in the aquaponic system. The aquaponic system was designed with a Poly Vinyl Chloride circular base of 10cm diameter perforated to produce a 5cm diameter hole made for the plant to float. Disposable plastic cup of 5cm diameter were filled with four growth media namely Palm kernel shells (PKS), Gravel (GRA), Crushed Snail Shell (CSS) and conventionally used loamy soil which was used as control to support the plants. Fish were fed for 56 days during which the water was recycled to serve as a source of nutrient for the plant. Water quality parameters were monitored throughout the experimental period and at the end of the experiment, yield of L. esculentum, growth performance and nutrient utilisation of H. bidorsalis were recorded. Significantly better (p<0.05) biometric parameters in terms of plant yield and fish zootechnical performance were recorded in H. bidorsalis and L. esculentum raised on the control, loamy soil and Palm kernel shells (PKS) in treatment one. This study showed that PKS is a suitable media bed in aquaponic for the production of tomatoes and H. bidorsalis. Palm kernel shells also enhanced the symbiotic integration of aquaculture and hydroponics in utilising waste as raw material to keep the aquaponic system sustainable and revolving.
Aquaponics is a form of sustainable agriculture that combines fish and plant in a closed recirculating system (FAO, 2016). A typical aquaponic system consists of a fish rearing tank, a solid removal tank, a biofilter, a hydroponic unit, and optionally a sump tank (Rakocy and Hargreaves, 1995). In aquaponic unit, water from the fish tank cycles through filters, plant grow beds and then back to the fish (Rakocy and Hargreaves, 1995).
The design of the aquaponics system used in the current study was a Pyramid Nutrient Film (PNF) Aquaponic System with a combined culture of Giant African catfish (Heterobranchus bidorsalis) and tomato (Lycopersicum esculentum). The aquaponic system was designed with plastic cup of 5cm diameter were filled with four growth media namely Palm kernel shells (PKS), Gravel (GRA), Crushed Snail Shell (CSS) and conventionally used loamy soil which was used as control to support the plants.
The water quality parameters monitored in the aquaponic system during the experimental period is shown in Table 1.
Discussion
The water quality parameters in the aquaponic system were within the recommended range for aquaculture (Ajani et al., 2011). The specific growth rates and feed conversion ratio observed in fish in the control were better than fish in other treatments. However, there was no significant difference in the SGR and FCR of fish in the control and PKS medium in treatment one. Although all the control treatments were significantly better in terms of plant and fish biotechnical performance than the other treatments, there was no significant difference between the control treatment and treatment one with the palm kernel growth media. This indicated that the protein contents of the experimental diets were effectively utilised to improve fish growth. This is in line with the findings of Oladimeji et al., (2020a) which stated that African catfish utilised protein in the aquaponic system better than conventional recirculatory and flow through systems.
Conclusion
This study demonstrated that non-conventional growth beds like palm kernel shell (PKS) is a suitable media bed in aquaponic production of tomatoes and giant African catfish.
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