The potential benefits of a recycling system incorporating membrane filtration have been demonstrated. The mRAS configuration as applied in this study demonstrated a good removal of the colloidal particulate fraction, reducing accumulation of these particles in the system, improved removal of nutrients and demonstrated a maturation effect on the biofilter. The overall results obtained demonstrated healthier cod larvae with higher growth and surviva lrates achieved. However, further studies are desired for long term research on other species like salmon and wrasse, from larvae to ongrowing stage, and in different designs and operating condition of an mRAS concept.