Production and control of fish health safely together with living in harmony with nature, natural substances considered as an important area for future developments in aquaculture. In this respect, the current study aimed to investigate the antibacterial activities of Trivir^®(10% carvacrol), one of the major essential oils of oregano, against some fish pathogenic bacteria isolated from diseased catfish (C. gariepinus). Trivir®solution was designated to be used as a broad-spectrum disinfectant for aquaculture according to the manufacture instructions. The antibacterial effects of the Trivir^®were tested on clinical isolates of Aeromonas hydrophila, Enterococcus faecalis and Shewanella putrificans. The minimum inhibitory concentrations (MICs) of carvacrol against Aeromonas hydrophila were estimated as 62 μg/ ml, 125μg/ml for Shewanella putrificans, and 250μg/ml for Enterococcus faecalis. At all tested levels, Trivir^®showed no bactericidal activities against all tested clinical bacterial isolates. C. gariepinus exposed to 32, 62, and 125 μg/ml of Trivir^®showed survival rates of 100% at all exposure times tested. In the contrast, Trivir® showed its toxic effects at concentrations of 1000, 500, 250 μg/ml after exposure times of 15, 30, and 60 min causing 100% mortalities in catfish. In conclusion, carvacrol can be considered as an effective alternative for antibiotics usage in aquaculture with ultimate competent health and a safe environment.