The impact of the different water qualities on the cod larva survival and growth in the two parallel systems is shown in Fig. 3.The cod larvae survival rates were investigated after 17 and 50 dph while the growth (measured by weight) is seen from 1 dph to 40 dph. A better performance was observed for the mRAS configuration with 3.5% average higher survival rate, and a significantly better performance with 13% higher growth rates (by weight) at 40 dph. The lower turbidity and number of colloidal particles inmRAS could possibly explain the higher cod larvae survival rateand cod larvae size experienced in the membrane filtrated tanks since colloidal particles can affect the gills thereby reducing the gill performance