The study of different levels of hardness and different rations of Ca and Mg water hardness on cyst hatching and larval quality of Artemia franciscana

Artemia is known as one of the most important species of living food needed in many larval stages in many aquatic animals. In this study, the effect of different levels of hardness on three levels (200, 500 and 100) mg.L and various ratios of calcium to magnesium (100: 0, 80:20, 50:50, 20:80 and 0: 100) on The percentage of hatching, total length and mortality rate of A. franciscana were determined. The results of different levels of hardness and various ratios of calcium and magnesium on the performance of A. franciscana showed that increasing the level of hardness is caused a decrease in the average percentage of hatching (P≤0.05), so that in the 1000 mg.L treatment, the lowest mean hatching rate was recorded as 31±7. In addition, the best ratio of calcium to magnesium ratio was 50:50. On the other hand, the effects of hardness levels and calcium and magnesium ratios on A.franciscana mortality rate showed that with increasing hardness were increased and calcium and magnesium ratios had no effect on mortality rates. Based on the results, the ratio of calcium to magnesium in the hardness 500 mg.l, had highest amount of hatching 73.33±2.35. Also, the hardness increasing caused a decrease in the size of the nauplii length and increased mortality.