This research was conducted in Gokcekaya Reservoir, which is located on the Sakarya River (Ankara, Turkey). Sediment samples were obtained before and after culture periods at a rainbow trout (Oncorhynchus mykiss) farm with a capacity of 950 t•y −1 . Total phosphorus (TP: 8.80 ± 0.50 and 9.10% ± 0.20%), total nitrogen (TN: 17.0 ± 0.20 and 17.05% ± 0.10%), organic matter (OM: 14.40 ± 0.40 and 14.60% ± 0.20%), redox potential (327.00 ± 0.08 and 170.00 ± 4.08 mV), water content (97.68 ± 0.28 and 96.38% ± 0.41%) and total organic carbon (TOC: 11.30 ± 0.10 and 13.40% ± 0.10%) were measured before and after the culture period, respectively. The mean rank order of sediment heavy metal was evaluated as Fe > Mn > Ni > Zn > Cr > Cu. The soluble reactive phosphorus (SRP) concentrations in the sediment pore water were 2.52 ± 0.14 and 7.75 ± 1.18 µg•L −1 (after the culture period, April 2012). The data on the sediment and the sediment pore water of the rainbow trout culture in Gokcekaya Reservoir shows that the cage culture in its present condition has no negative effect on sediment quality.