The study investigated the circadian rhythm and ammonium and phosphorus excretion rates (AER and PER) of sandfish at salinity levels of 20, 26, and 32 ppt. Results demonstrated a bimodal circadian rhythm in AER with peaks at 0030H and 0830H, while the PER values were too low to be deemed significant. AER showed a significant correlation with body weight at 26 and 32 ppt, indicating a response to salinity stress, with lower AER at 26 ppt suggesting energy conservation and limited metabolic functions.