The study presents the assessment of water quality of a recirculation aquaculture system (RAS). In this study, a laboratory- scale recirculation aquaculture plant was designed and fabricated to reduce, recycle and reuse fish farm wastewater. The system incorporates trickling filter as a biological treatment processes. Development of bacteria on the trickling filter was done by continuous recirculation of highly concentrated fish farm waste water for 16 days when a considerable mass of bacteria enough for nitrification was observed to have developed. In the experiment, two different systems were compared: a RAS with trickling filter and a conventional open pond system. A sample of effluent from the trickling filter was analyzed for ammonia, nitrite, nitrate, dissolved oxygen, pH and total suspended solid. The result of the analysis showed that the water parameters in RAS were within acceptable level for African catfish culture; 32.89L of water was used up in the RAS for the 21 days culture and percentage increase in weight ranging from 17.69% - 37.05% was observed in the RAS. This shows that the system was effective in producing required effluent quality for catfish fish rearing.