The effect of long-term exposure to single and mixed mineral ions related to water hardness on Nile tilapia (Oreochromis Niloticus).

The current study aimed to evaluate the harmful effects of single and mixed minerals involved in water hardness on Nile tilapia (Oreochromis niloticus). Seventy-five fish were randomly assigned to five groups (n = 15), each consisting of three replicates (n = 5), and subjected to the following treatments for two months: standard fishery water, Ca (186 mg/L CaCl₂), Mg (40 mg/L MgCl₂), Na (25 g/L NaHCO₃), a mixture of MgCl₂, CaCl₂, and NaHCO₃ at the same protocol dosing to adjust water hardness at 300 mg/L. The results reported that fish exposed to Ca, Na, and Mix salts showed a significant decline in growth performance, serum antioxidant levels, and protein profile along with a significant rise in the enzymatic activity of ALT, AST, urea, creatinine, and MDA levels (P ≤ 0.05). Exposure of fish to either single or mixed ions caused histopathological changes in the gills, liver, kidney, spleen, and brain. However, the nature, distribution, and the degree of severity of histopathological lesions vary in the experimental groups. The group exposed to mixed salts had the highest scores in all the pathological parameters, whereas the Mg group recorded the lowest scores. Moreover, the Ca group exhibited the highest scores in the liver and kidney, while the Na group showed the highest scores in the gills, spleen, and kidney.