Effect of probiotic dosage on fish growth, water quality, and microbial composition in aquaponics systems at Jimma University, Jimma, Ethiopia

Title : Effect of probiotic dosage on fish growth, water quality, and microbial composition in aquaponics systems at Jimma University, Jimma, Ethiopia

Abstract:

Probiotics play a vital role in enhancing immunity, combating pathogens, and reducing the impact of antibiotics in aquaculture. However, studies on optimal probiotic dosages remain limited. This study evaluated the effects of mixed probiotics on fish growth, water quality, and microbial composition in an aquaponics system. A total of 36 Clarias gariepinus (initial weight: 41.53 ± 3.88 g, p > 0.05) were collected from a reservoir, stocked in six identical tanks, and fed at 5% body weight twice daily. Probiotics were isolated from African catfish, screened and administered in basal diets for three treatments at ratios of 1:2:3 and monitored for 60 days. Additionally, 192 lettuce seedlings were transplanted into six hydroponic units with initial parameters at p > 0.05 and evaluated over five weeks. The collected data from aquaponics system were analyzed using one-way ANOVA and Duncan’s test. The highest fish weight was recorded in T₂ (122.67 ± 5.19 g), followed by T₃ (118.17 ± 8.30 g) and T₁ (112.17 ± 8.79 g/fish). Performance metrics ranged as follows: daily weight gain (1.18–1.36 g/day), percentage weight gain (169.19–196.81%), feed conversion ratio (1.11–1.02), feed efficiency (90.03–98.46%), specific growth rate (1.65–1.82%/fish/day), and a consistent survival rate (100%). While no significant differences (p > 0.05) were observed between T2 and T3, both outperformed T1 (p < 0.05). Water quality parameters showed no significant differences (p > 0.05) between treatments. Nitrogen compounds were highest in fish tanks, followed by biofilters and hydroponics units, except for nitrates, which peaked in biofilter outlets. Lettuce biomass was highest in T₃ (672 ± 177.09 g), followed by T₂ (624 ± 61.14 g) and T₁ (602 ± 99.08 g). Microbial loads in water were highest in T1 (68.33 ± 27.27 CFU/mL), followed by T2 (57.67 ± 19.62 CFU/mL) and T3 (54.83 ± 16.02 CFU/mL). Microbial loads in fish tissues were highest in the stomach, followed by the skin and gills, with higher values in T₁ compared to T₂ and T₃. In conclusion, increasing probiotic dosage improves fish growth, enhances water quality, reduces toxic nitrogen compounds, and boosts nitrate levels, ultimately supporting higher lettuce biomass and fostering balanced ecosystems in aquaponics systems.
Key Words: Aquaponics, Fish Growth, Lettuce Biomass, Microbial Composition, Probiotics, Water Quality.

Biography:

Firew Admasu studied B.Ed. degree in Biology with minor chemistry, and M.Sc. degree in Biology (Ecological and systematic zoology). He then joined Dilla University as a lecturer of Biology (Ecological and Systematic Zoology) at the Department of Biology, College of Natural Sciences, with affluent experiences in both teaching and research. He has published more than 10 research articles in different journals. Now, he is a Ph.D. Candidate in Biology (Aquaculture and Fisheries Management) at Jimma University, Ethiopia.