Water quality plays a significant role in the biology and physiology of fish and may impact on the health and productivity of the culture system (Boyd, 1997 and Landau, 1992). Throughout this experiment, water quality across all the treatments was within the favorable range required for tilapia (Boyd, 1997); the variation in fish growth in this study may not therefore be strictly attributed to the characteristics of water quality parameters.
In conclusion, the results indicate that the improved F6 and F5 strains have lower FCR and thus are more efficient at utilizing feed and growing better than the unimproved strain at stocking densities of 5 fish/m3. These results support recommended Tilapia stocking densities that take into account transport and handling related mortalities (Russell et al., 2008) and should be practical for most small holder farmers in Malawi.