Danio rerio Hamilton, 1822 is one of the commercial ornamental fresh water fishes and living in tropical zones, of considerable economic value in our country. This study aimed at investigating the impact of Spirulina sp. on index color in Danio rerio. 360 individuals were randomly divided in 12 aquariums with 4 treatments and 3 replications. The dietary treatments included treatment 1 or control (commercial food with no supplement of Spirulina sp.), treatment 2 (commercial food with 0.5% supplement of Spirulina sp.), treatment 3 (commercial food with 1% supplement of Spirulina sp.) and treatment 4 (commercial food with 1.5% supplement of Spirulina sp.). In general, the use of Spirulina sp. in the diet of Danio rerio caused increase in body weight and specific growth rate, but increasing the amount of dietary of Spirulina sp. powder in the diet of Danio rerio during the breeding period of 60 days had no impact on the feed conversion ratio. There being no significant difference between treatments 1% and 1.5 %, treatment 1% of supplement Spirulina sp. was found to be the best treatment for growth in Danio rerio.

Special properties and various applications of Spirulina species have led to the growing focus of biotechnology to the cost effective cultivation. Open ponds used in the most commercial cultivation have many deficiencies such as risk of contamination, lack of light penetration, inefficient mixing and low productivity. In this study, an innovative reactor was designed and manufactured. By adding a control area, it was possible to control some environmental conditions for a limited amount of open pond volume. The conventional pumping system was replaced by a new elevator system to reduce the damage of to the fragile cells. The baffles structure and aeration from bottom, contributed to better mixing system. The effect of tree factors (Circulation Cycle (Cir. Cyc.), Control Volume (Con.Vol.) and Irradiance Intensity (Irr. Int.) in units of hours, percentage and Lux respectively) on the quantity of biomass (Specific Growth Rate (SGR, day^-1) and fifth and seventh day dry weight (g/L)) were evaluated using RSM-CCD. The maximum biomass dry weight (0.915 g/L) was achieved in longest circulation cycle (12 hours), 30% Con. Vol. and 7000 Lux light intensity. The optimal irradiance intensity to achieve the highest biomass was 8700 Lux. According to the results, due to the great influence of Con. Vol. and Cir. Cyc., it is possible to increase the productivity and enhance the culture dry weight by controlling a limited amount of ponds volume (20%), subject to economic considerations. These successful results can provide the context using a control zone for several open ponds to improve the overall efficiency.