Abstract: In this study, effect of dietary supplementation of different rates (10% Group B, 20% Group C, 30% Group D, 40% Group E) of spirulina (Spirulina platensis) on growth and feed conversion in guppy (Poecilia reticulata) was compared with a commercial stamp food (Group A). Fish fed 40% spirulina performed better than those fed lower levels. At the end of the experiment, there were no significant differences between the all groups in terms of average final weights (p>0.05). No significant differences were observed in specific growth rate, feed conversion rate and weight gain. However, there were significant differences in terms of feed conversion rate between groups (p<0.05) and it was the highest in Group E (1.090±0.044) and the lowest in Group A (2.312±0.071). Therefore, the best growth rate (1.933±0.009) and live weight gain (0.085±0.006 ) were recorded in Group