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The performance of lava stones as water treatment media in the culture of African catfish (Clarias gariepinus) was investigated. Catfish fingerlings of mean weight 4.7g were stocked in replicates at 32 kg/m3 and reared for 35 days in a recirculating aquaculture system (RAS) facilities with lava stones as biofilter media. The stones were stacked in bottle slots in plastic lemonade crates creating a surface area between 110-160 m2/m3 with average open pore area of 68% and a dry weight of between 36 – 44 kg/m3. Water samples were taken for quality assessment from the various components twice per week to assess the level of suspended solids (SS), nitrite-nitrogen (NO2-N), nitrate-nitrogen (NO3-N) and dissolved oxygen (DO).
Lava stone was efficient in oxidizing ammonia and maintaining DO in rearing tanks within the acceptable safe limits for the optimum survival and growth rate of cultured fish. The production per cubic metre of water, 60.7kg achieved compares well with the range of 28 kg/m3 to 114 kg/m3 recommended for stable RAS operation. The FCR recorded are above the ideal value of 1.0 for culture of African catfish in recirculating system. The results show that lava stones can serve well for water treatment in the culture of African catfish fingerlings in RAS if all operational and maintenance needs for the media can be met.
Keywords: Lava stone, biofilter, recirculation, production
African Journal of Livestock Extension Vol. 4 2005: pp. 24-28