Each extract was tested in triplicate. Negative
controls were prepared in the same way except that 40 μl of pure solvents were used
instead of the herb extracts. Oxytetracycline (5 μg on sterile paper disc), a common
antibiotic used in tilapia aquaculture in Thailand, served as the positive control. The
prepared agar plates were then incubated at 25 °C for 18 h,