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The present study was conducted to investigate the effect of the diet containing Laurencia caspica (red algae) on blood parameters and digestive enzymes activity of goldfish after 90-day period. Goldfish (weight 6.10±0.1 gr) were divided to four experimental groups (30 individuals in each replication) including experimental treatment of the control group (without using red algae) and three treatments by adding 5, 10, and 20 grams of red algae to kilogram of diet. The results of the experiment showed that all hematological indices (red blood cells, white blood cells, hemoglobin, and hematocrit) in fish fed with algae significantly increased compared to the control group (P < 0.05). Among the blood biochemical indices, there were a significant difference in the triglycerides and cholesterol (P < 0.05). The highest activities of the digestive enzymes were observed in the treatment containing 20 grams of algae per kilogram of diet (P < 0.05) including amylase (620.26± 4.10 U/mg protein), lipase (19 ± 1.17 U/mg protein), and protease (290.11 ± 3.20 U/mg protein). Overall, the results of the study showed that there was a significant improvement in blood indices and the activity of digestion enzymes with the use of a diet containing 20 grams of red algae per kilogram of goldfish diet and therefore this diet is recommended.