Sustainable Water Management in Aquaculture: Comparing Eco-Friendly and Conventional Treatment Strategies (Fish Farm)

This study investigated the comparative effects of natural and chemical treatments on pond water samples obtained from the AAUA Fishery, with emphasis on microbial load reduction, diversity, antibiotic susceptibility, fungal occurrence, and molecular resistance gene detection. Treatments applied included <i>Moringa oleifera</i> leaf powder (0.5 g and 1 g), chlorine (0.5 g and 1 g), and direct sunlight exposure, while untreated samples served as controls. Microbiological analyses were performed using serial dilution, spread plating, colony morphology, Gram staining, and biochemical characterization, with bacterial identification supported by Bergey’s Manual of Determinative Bacteriology. Fungal isolates were identified based on cultural and microscopic features, and antibiotic susceptibility was assessed using the Kirby–Bauer disk diffusion method. PCR amplification was used to detect selected antibiotic resistance genes. Results showed that 0.5 g of <i>Moringa</i> moderately reduced bacterial counts from 3.5 × 10<sup>4</sup> to 7.0 × 10<sup>3</sup> CFU/mL (10<sup>-3</sup> dilution) and from 2.0 × 10<sup>7</sup> to 6.0 × 10<sup>6</sup> CFU/mL (10<sup>-6</sup> dilution) over 6 h, while 1 g produced weaker inhibition. Sunlight treatment was more effective, lowering bacterial load from 6.0 × 10<sup>4</sup> to 7.0 × 10<sup>3</sup> CFU/mL and from 3.5 × 10<sup>7</sup> to 4.0 × 10<sup>6</sup> CFU/mL across dilutions. Chlorine was the most potent treatment, achieving complete elimination of bacterial growth within 4–6 h at both concentrations. Control samples only showed a natural decline in bacterial counts. Biochemical and colony analyses revealed diverse bacterial species, including <i>Staphylococcus aureus</i>, <i>Micrococcus luteus</i>, <i>Bacillus</i> spp., <i>Aeromonas hydrophila</i>, <i>Enterococcus faecalis</i>, <i>Corynebacterium</i> sp., <i>Vibrio cholerae</i>, and <i>Listeria monocytogenes</i>. Antibiotic susceptibility tests indicated that both Gram-positive and Gram-negative isolates exhibited multidrug resistance, with inhibition zones ranging between 10 mm and 16 mm. Fungal isolates included <i>Aspergillus fumigatus</i>, <i>Aspergillus terreus</i>, <i>Aspergillus sydowii</i>, <i>Eurotium</i> sp., and <i>Aspergillus flavus</i>. Molecular assays detected the presence of blaOXA and qnrA resistance genes, while blaNDM, blaTEM, blaSHV, tetA, tetB, and cmlA were not detected. These findings highlight the superior bactericidal effect of chlorine relative to <i>Moringa oleifera</i> and sunlight, <i>Moringa oleifera</i> become an alternative source to chlorine and its effects on multidrug resistant microorganisms in pond water, but also reveal the persistence of multidrug-resistant bacteria and fungi in treated pond water. The study underscores the need for integrated water treatment approaches and continuous monitoring to safeguard aquaculture productivity and public health.