Cage culture of Etroplus suratensis (Pearlspot) was carried out in Krishnagiri reservoir (12°29′20″N 75°53′51″E), constructed across the River Ponnaiyar in Tamilnadu. E. suratensis an indigenous cichlid, native to peninsular India is a highly priced species in Kerala. The fishes of average weight 5.98 ± 0.52g were stocked at the rate of 10nos/m3 in High Density Poly Ethylene (HDPE) floating cages (3x3x2m) made of 210D nylon knotless net with a mesh size of 12 mm. Fishes were fed commercial pellet feed containing 32% protein at the rate of 5-3% of body weight twice a day. Water quality and growth was monitored in regular intervals. A reference point (N 12˚29ˈ 8.21'' E 78˚10ˈ29.46'') was fixed at 100 m away from the cage site to compare the water quality as well as plankton abundance between cage site and reference site to understand the difference. After 6 months of culture the fishes grew to 68.28 ± 0.35g with a mean weight gain of 62.3g. During the first two months of culture the mean weight gain was low, with a steady increase for the rest of the culture period. Percentage weight gain, specific growth rate, food conversion ratio, feed efficiency ratio and protein efficiency ratio of the fishes after 6 months was observed to be 1041.8 ±1.41%, 1.16±0.04, 2.35±0.02, 0.42±0.01 and 1.32±0.01 respectively. Overall the growth of Etroplus in terms of the analysed parameters was found to be satisfactory in freshwater cages irrespective of the low survival (52%). Water temperature was recorded to be in the range of 24.7-32.50C during the culture period. Transparency ranged from less 0.4m to 0.5m. Dissolved oxygen content was found to be 6 to 13.9 ppm and pH in the range of 8.15 to 9.5. The values for alkalinity and electrical conductivity ranged from 202 to 224ppm and 1130 to 1236 µs/cm respectively. Comparison of plankton abundance between cage site and reference site showed that zooplankton density (no. of individuals/litre) at cage site (91.67a±6.66, 422.33a±12.66, 574.01a±4.58 during 1st, 3rd and 7th month respectively) is significantly higher than the reference site (67.17b±6.66, 232.66b±10.02, 452.05b±9.21 during 1st, 3rd and 7th month respectively) throughout the observation period. Likewise phytoplankton density (no. of cells/litre) at cage site (152283a±134.63, 437546a±56.86, 226513a±23.09 during 1st, 3rd and 7th month respectively) was also found to be significantly higher than the reference site (112243b±40.42, 330516b±67.62, 148286b±175.94 during 1st, 3rd and 7th month respectively) throughout the observation period. The high density of plankton at cage site may be due to the availability of primary nutrients derived from the decomposition of leftover feed from the cage.