Abstract: The study focused on mud carp, employing varying concentrations of copper sulfate solutions to replicate the medicated bathing process. Over the 7-day experimental period, the mortality count, body length, and weight of deceased fish were recorded at 24-hour intervals. The semi-lethal concentration (LC₅₀) was determined through the direct regression method, alongside the corresponding safety concentration (SC) and toxicity accumulation (MAC). Pre- and post-experiment, copper ion concentrations in the water were assessed in post-experiment, using atomic absorption spectrophotometry and ultraviolet-visible spectrophotometry, respectively. The cumulative mortality (expressed in probability units) of mud carp fry in the copper sulfate solution demonstrated a positive linear correlation with the logarithm of copper sulfate concentration. LC₅₀ and SC for a 24-hour immersion were established at 1.461 2 and 0.146 1 mg/L, respectively, gradually decreasing thereafter. The toxicity accumulation curve exhibited an S-shape. Copper ion concentration in the water decreased compared to pre-experiment levels, indicating copper sulfate accumulation in mud carp bodies. Given the pronounced acute toxicity of copper sulfate to mud carp, categorizing it as a highly toxic pesticide, and considering the poor tolerance of mud carp to copper sulfate, a recommended approach in practical production involves utilizing a high-concentration and short-duration bathing method.