Evaluation of the presence and efficiency of potential probiotic bacteria in the gut of tilapia (Oreochromis niloticus) using the fluorescent in situ hybridization technique

► Endemic probiotic Bacillus sp. was used to control tilapia pathogenic bacteria. ► FISH is a powerful tool to evaluate the probiotic bacteria candidates in fish guts. ► Decrease of pathogen number showed the probiotic efficiency in tilapia juvenile.