Lowering of the gut pH with dietary KDF has an eubiotic effect on the allochthonous, beneficial lactic acid bacteria. This was significantly detected in the LAB count of the fish group fed 0.3% KDF. The LAB count was elevated from 23 × 102 CFU/g in the control group to 24 × 103 CFU/g. Lactic acid bacteria are able to grow at a relatively low pH, which means that they are more resistant to organic acids/salts than gram-negative bacteria [13]. These indigenous probiotic bacteria have the ability to colonise the intestinal surface and form a barrier, serving as the first defence to limit direct attachment or interaction of fish pathogenic bacteria to the gut mucosa [15]. It was reported that dietary KDF stimulates the colonisation of certain gut bacteria and inhibits the growth of others in hybrid tilapia [3]. It improved the relative richness of certain intestinal allochthonous bacteria, such as Mycobacterium sp. Partial MHSD12-like, Mycobacterium peregrinum-like, Pseudomonas sp. HMPB4-like and six uncultured bacterium like species. However, alpha Proteobacterium IMCC1702-like, Rhodococcus sp. P14-like, and three uncultured bacterium-like species were depressed in the gut. Similarly, Owen et al. [31] reported the tendency for a relative increase in the proportion of gram-positive bacteria of Clarias gariepinus treated with sodium butyrate. The eubiotic effect of KDF on the proliferation of indigenous probionts may be the third reason for improving the growth performance because this gram-positive bacterium plays a vital role in fermentation of certain non-digestible carbohydrates and increases the availability of nutrients [15].