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¹ Fish Ecology Department, Central Laboratory of Aquaculture Research, Abbassa, Abo-Hammad, Sharqia, Egypt Viewed : 4283 - Downloaded : 2927 A growth response study was carried out to evaluate the influence of artificially submerged macrophytes on growth performance and supplemental feed utilization of Nile tilapia, Oreochromis niloticus (L.) fry under aquarium conditions. In glass aquarium (80 x 50 x 50 cm) filled with 140 litres of well-aerated tap water (25 to 28 ºC), leafless stems of phragmites plant (0.7 m long and 0.5 cm diameter) were used at densities of 0, 25, 50, 75, 100 and 125 stems/m². The final fish weight, weight gain and specific growth rate (SGR) decreased significantly with the increase in plant density (P<0.05). The lowest fish growth was obtained at densities over 75 stems/ m². The higher feed intake was recorded at control, while the lowest one was obtained at densities of 75-125 stems/m2 (P<0.05). In contrast, feed conversion ratio (FCR) was only higher at the density of 125 stems/m² (P<0.05). The protein efficiency ratio (PER), protein productive value (PPV) and protein growth rate (PGR) declined significantly at the density of 125 stems/m² (P<0.05). Contents of moisture and crude protein in whole fish body increased slightly with the increase in plant density (P>0.05). The total lipid content was only decreased, while ash content increased significantly at plant density of 125 stems/m². It could be recommended that submerged macrophytes, used as fish refuges from predators or for periphyton production, should be at low or moderate density, however, dense vegetation reduces significantly fish growth and feed utilization. Keywords : Aquatic vegetation, Nile tilapia, growth, feed utilization, feed conversion ratio, protein efficiency ratio, protein growth rate