Investigating the impact of external application of formalin and potassium permanganate on hematological, immunological, and biochemical profiles in Labeo rohita fingerlings.

The present study aimed to elucidate the suitability of formalin and KMnO₄ as therapeutics for fish diseases in Indian major carp, Labeo rohita, while considering their impact on fish stress levels. Acute toxicity tests revealed that the 96-hour LC₅₀ values for formalin and KMnO₄ were 66.58 ppm and 2.89 ppm, respectively. Sub-lethal concentrations of formalin (6.65 ppm, 3.32 ppm, and 2.21 ppm) and KMnO₄ (0.289 ppm, 0.145 ppm, and 0.096 ppm), along with control groups, were administered to the fish for different exposure periods (24, 48, 72, and 96 hours) and different hematological, biochemical, and immunological parameters were analyzed. The findings demonstrated that formalin exposure resulted in a significant decrease (p < 0.05) in hematological parameters, immunological parameters, and serum protein levels. Conversely, formalin exposure led to significant increases (p < 0.05) in serum glucose, SGOT, SGPT, and ALP levels. In contrast, KMnO₄ exposure significantly decreased (p < 0.05) hematological parameters and serum protein levels, while significantly increasing (p < 0.05) immunological parameters. To evaluate curative efficacy, challenge studies were conducted using three sub-lethal concentrations of formalin and KMnO₄ against Aeromonas hydrophila (ATCC 7966) infection. Based on the aforementioned results, the recommended doses of formalin and KMnO₄ were found to be 6.65 ppm and 0.289 ppm, respectively.