INVESTIGATING THE MICROBIAL COMMUNITY INVOLVED IN THE DECOMPOSITION OF ORGANIC MATTER IN CATFISH POND WASTEWATER

ABSTRACT Aquaculture especially catfish farming produces large amounts of organic waste from uneaten feed, fish excreta and decaying biomass. Microbial communities drive the breakdown of this waste, thereby recycling nutrients, stabilizing water quality and sustaining pond ecology. This study investigated those communities in catfish pond wastewater by identifying dominant bacteria and fungi, quantifying their populations and relating microbial activity to key water quality parameters. Water (surface, mid depth, bottom) and sediment samples were collected on Day 2 and Day 7; isolates were cultured on Nutrient Agar and Potato Dextrose Agar, identified by colony morphology, Gram staining and basic biochemical tests, and enumerated as colony forming units (CFU). Physicochemical parameters (pH, dissolved oxygen, ammonia and temperature) were recorded in situ. Sterile water served as an external control. Results showed a diverse community dominated by Bacillus spp., Pseudomonas spp., Aeromonas spp., Aspergillus and Penicillium. Quantitatively, Wastewater Day 2 (control) contained 2.1 × 10⁵ CFU mL⁻¹ bacteria and 1.6 × 10³ CFU mL⁻¹ fungi. By Wastewater Day 7 these counts had more than doubled to 4.8 × 10⁵ CFU mL⁻¹ and 3.3 × 10³ CFU mL⁻¹, respectively, while Sediment Day 7 recorded the highest loads—1.1 × 10⁶ CFU g⁻¹ bacteria and 5.9 × 10³ CFU g⁻¹ fungi—consistent with intensified decomposition in the low oxygen pond bottom. Correspondingly, dissolved oxygen levels fell from 6.2 mg L⁻¹ on Day 2 to 4.1 mg L⁻¹ on Day 7, while ammonia rose from 0.28 to 0.73 mg L⁻¹. These data confirm that microbial activity—and therefore waste degradation—progresses rapidly within the first week after waste input, especially in sediments. Understanding these dynamics provides a basis for low cost management practices (e.g., controlled feeding, probiotic supplementation, periodic sludge removal) that harness natural microbiota to maintain water quality and promote sustainable catfish production. This study highlights the importance of microbial communities in regulating pond wastewater quality and provides insights into optimizing natural decomposition processes for sustainable aquaculture management