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Effect of growth substrates on water quality, catfish culture and spinach propagation under aquaponic system

Modern technologies such as aquaponic system should be embraced to capitalize on fish and crop production. pumice, charcoal and a homogeneous mixture of (pumice and charcoal) were used as substrates and assessed on a control (aeroponic) for their suitability in nutrients removal from water for C. gariepinus culture and S. oleracea propagation under aquaponic system. Specified water parameters in fish tanks; the inlets and outlets of the hydroponic units, were determined in-situ and in the laboratory.

C. gariepinus post fingerlings weighing 14.97±0.5g and length 14.05±0.5cm were stocked at 50 fish/tank in 12, 1000L tanks under aquaponic system. Experimental fish were subjected to the same diet that was analyzed for its proximate composition and found to contain 35% crude proteins content (CP). Fish were sampled after every three weeks while mortality was recorded on occurrence.

The outcome of the trials on water quality, C. gariepinus growth performance and survival rates revealed statistical variation (p<0.05) for the treatments used. The pumice substrate had better performance in percentage nutrients reduction for the nutrients analyzed, followed by the mixture of pumice charcoal substate. Charcoal substrate outperformed the other treatments in percentage reduction efficiency for phosphates.

The control treatment was the least in percentage reduction efficiency. Mean weight gained by fish for the treatments differed statistically at (p<0.05) with weight gains of 93.81g, 77.57g, 69.79g and 55.37g for pumice, pumice charcoal, charcoal and control treatments respectively.

The survival rates ranged between 92-98%. S. oleracea performed better under a mixture of pumice and charcoal treatment in comparison to the other treatments under the present study. Results from this study suggest that nutrient reduction efficiency can be increased by replicating the hydroponic units with appropriate substrate to increase retention time of water in the hydroponic for increased fish and crops production.

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