This study was carried out on three different species of fish (Tilapia Zillii (T.z), Oreochromis galileus (O.g) and Oreochromis niloticus (0.n), respectively, stocked by mono and polyculture systems. Analysis of variance of the obtained data showed that the stocking system significantly affect the T. cholesterol, T. lipids, urea, ALP and LDH levels in sera of examined fish. While, the species, stocking system interaction significantly influenced the all studied parameters. The greatest values of T. proteins, albumin, globulins, T. cholesterol, T. lipids, Urea, ALP and LDH were observed in T. zillii monoculture followed by T. zillii polyculture.