Copper Sulfate (CuSO4) is the most used in aquaculture as chemotherapeutic bath against bacterial, fungal and parasitic diseases but it is very toxic for fish so the goal of this study was to determine the lethal concentration of CuSO4 and evaluate it is toxicity in the gill and central nervous system (brain and spinal cord) in Cyprinus carpio. Fish exposed to 0, 2.5, 5 and 10 mg/L for 24 hours, each concentration with three replication each have six fish. The mortality rate was 100% at concentration 10 mg/L, which represented lethal concentration, while medium lethal concentration (LC50) was determined by Trevan method and it is 5mg/L. The fish with LC100 concentration exhibit abnormal respiration with gasping swimming, nervous sings with up down and stay at basin then die at 2-3 hours. The histopathological examination of the gills revealed circulatory disturbances, cellularity reaction, progressive and regressive alteration, this microscopic alteration was evaluated as semi-quantities analysis and there was variable significant (P≤0.05) in the pathological alteration and gill indexes between two treatments. In the brain and spinal cord, the lesions are represented by vasogenic edema, infiltration of inflammatory cells with atrophy in the neuronal body cells and hemorrhage. It is concluded from this study that the use of copper sulfate is within limited concentrations because increasing its concentration leads to fish toxicity, and it was observed that the gill tissue is more sensitive to toxicity than the central nervous system.

This current study aimed to study the effect of adding blue-green algae (Spirulina), symbiotic (poultry star ® me) at a ratio of 1 to 2% and colistin antibiotic to the control diet of common carp fish reared in glass aquariums for 56 days terms of three replicates for each treatment. The growth results showed that the fish fed on the third diet was significantly superior to the fish fed on the other experimental diets in the rate of total and daily weight gain, feed conversion ratio, feeding efficiency ratio and protein efficiency ratio criteria over all other experimental diets except for the second diet, 1% spirulina. The fish fed on the second diet significantly outperformed in the precipitated protein criterion and the protein productive value of all the experimental diets under study. The value of crude protein in the edible portion increased significantly when fish were fed on spirulina, symbiotic and antibiotic diets, compared to the control diet, while the percentage of fats in the fish fed on diets containing the food additives under test decreased significantly compared to the control diet. No significant differences were recorded in the percentage of ash. It is evident from what was mentioned above that the best results of the studied criteria were when adding spirulina at had positive effects on growth criteria and food utilization.

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